Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.

All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group, [] contains explanatory material, () features common in clade, exact status unclear.

Note: Possible apomorphies are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned
is unclear. This is partly because many characters show considerable homoplasy, in addition, basic information for all too many is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there is the not-so-trivial issue of how ancestral states are reconstructed (see above).

Evolution.Divergence & Distribution. Asparagales may have the highest diversification rate in the monocots, about the same as Poales, but in both the rate is little over half that of Lamiales, the clade with the highest rate (Magallón & Castillo 2009); Magallón and Sanderson (2001) did not give estimates for the group. Within the clade, the diversity of Orchidaceae is indeed remarkable, but its sister taxon is all other Asparagales, somewhat less species-rich, perhaps, but a morphologically motley crew (see also below, under Orchidaceae). And sister to Asparagales are the commelinids, so it is not totally clear what such figures suggest (see below).

S. Chen et al. (2013) give age estimates for many nodes in Asparagales in particular, but differences between the two methods that they used (PATHd8 and BEAST) were often substantial, the older ages being about half as much again as the younger age (PATHd8) in a third or so cases.

Bacterial/Fungal Associations. Asparagales commonly have Arum-type arbuscular mycorrhizae where the hyphae are intercellular, and also form coils, pelotons and particularly branched arbuscules within cells, while in Liliales these mycorrhizae are commonly Paris-type with intercellular hyphae that form coiled structures between the cells (see F. A. Smith & Smith 1997; Rasmussen & Rasmussen 2014).

Chemistry, Morphology, etc. Storage mannans in the vegetative tissues are reported from Xanthorrhoeaceae-Asphodeloideae, Amaryllidaceae and Orchidaceae; they are uncommon elsewhere (Meier & Reid 1982). Mucilage polysaccharides in the roots of Asparagaceae-Asparagoideae may also have a storage role. There is no starch in the chloroplasts of members of Amaryllidaceae, Iridaceae, and "Liliaceae" (?= Allium) and no chloroplasts at all (although there are other plastid-type structures) in some Orchidaceae (Willmer & Fricker 1996).

Three-trace tepals are found in Orchidaceae, Amaryllidaceae-Amaryllidoideae and -Agapanthoideae, Iridaceae, Xanthorrhoeaceae-Asphodeloideae (but not Kniphofia, Ashpodelus) and -Hemerocallidoideae, Asparagaceae-Agavoideae; one-trace tepals in Amaryllidaceae-Allioideae and Asparagaceae-Nolinoideae (but not Maianthemum stellatum), -Aphyllanthoideae, and -Asparagoideae. Asparagaceae-Scilloideae have tepals with both one and three traces, Urginea even having five traces in the outer whorls (see especially Chatin 1920). Where changes in microsporogenesis are to be placed on the tree is not clear. Furthermore, Rudall (2001a, see also 2002, 2003a) included an inferior ovary as a synapomorphy of the order, noting that in "higher" Asparagales there might be a reversal to superior ovaries that is associated with the presence of infralocular septal nectaries (as in Xanthorrhoea and Johnsonia (Xanthorrhoeaceae-Xanthorrhoeoideae and -Hemerocallidoideae). However, since superior ovaries are also scattered through the "lower" Asparagales, fitting ovary evolution to the tree is difficult; ovary position seems a much more flexible character here (and elsewhere) than it has generally been given credit for.

For flavonoids, see Williams et al. 1988), for general morphology, see Rudall (2003a), for root morphology, see Kauff et al. (2000), for cladodes, see Schlittler (1953b), for inflorescences, see Schlittler (1953a), for pollen of Japanese representatives, see Handa et al. (2001), for ovule and seed, see Shamrov (1999a) and Oganezova (2000a, b), for cytology, see Tamura (1995), for cytology and genome size, see Pires et al. (2006), and for the distribution of taxa with phytomelan and/or with baccate fruits, see Rasmussen et al. (2006).

Phylogeny. For discussion on the relationships of Asparagales, see Petrosaviales.

The tree (below) of relationships within Asparagales is based largely on the analyses in Chase et al. (2000a) and Fay et al. (2000: successive weighting). These studies differ little in detail, although the analysis of Fay et al. (2000) hardly suprisingly had more nodes in the core Asparagales with strong support. For the Amaryllidaceae + Agapanthaceae node, see Meerow et al. (2000b), and relationships between Aphyllanthaceae, Themidaceae and Hyacinthaceae might be better represented as trichotomy (see also S. Chen et al. 2013); these families are now subsumed in a broadly-drawn Amaryllidaceae and Asparagaceae respectively. The relationships in McPherson and Graham (2001) and D.-K. Kim et al. (2012) are largely congruent with the tree below, although their sampling is poorer and more geographically constrained.

Understanding the relationships between Boryaceae and Orchidaceae is important. Boryaceae have been placed as sister to
Orchidaceae (e.g. Chase et al. 1995a; McPherson & Graham 2001), although with rather weak support. A [Boryaceae, Blandfordiaceae, etc.] clade were sister to other Asparagales in Janssen and Bremer (2004), with relationships above Orchidaceae being pectinate - [Orchidaceae [Ixoliriaceae [Tecophilaeaceae [Doryanthaceae + The Rest]]]]. Orchidaceae were embedded in a paraphyletic Boryaceae-Hypoxidaceae clade (Li & Zhou 2007), but again, with little support. In Wikström et al. (2001) Orchidaceae were sister to Hypoxidaceae. Seberg et al. (2012: mitochondrial and chloroplast data agreed only after removing edited mitochondrial sites) largely recovered the topology found by earlier workers; mitochondrial data provided little support for the backbone of the tree.

Recent work suggests that Orchidaceae are sister to other Asparagales (e.g. 76% bootstrap support in Graham et al. 2006; about the same in Givnish et al. 2006b; stronger [96-99%] in Pires et al. 2006: good sampling, seven genes from two compartments; S. Chen et al. 2013). There was more or less strong support for the [Boryaceae, Blandfordiaceae et al.] clade in these analyses, although a clade [Asteliaceae [Lanariaceae + Hypoxidaceae]] was recovered by S. Chen et al. (2013). While there is good support in Chase et al. (2006) for Orchidaceae being sister to all other Asparagales, Boryaceae were placed immediately above the Blandfordiaceae et al. clade, albeit with very little support. In some phylogenetic reconstructions of Hilu et al. (2003) Asparagales were paraphyletic, Orchidaceae being separate from the rest. Rudall (2003a: morphological data) suggested that there was a close relationship between Hypoxidaceae and Orchidaceae in particular, and also between Boryaceae and Blandfordiaceae and Iridaceae and Doryanthaceae. All in all, the topology [Orchidaceae [[Boryaceae, Blandfordiaceae et al.] [all other Asparagales]]], seems the best hypothesis. This affects the characterisation of Asparagales, since some characters previously considered to refer to the clade as a whole now move to the subbasal node in the tree (c.f. versions 6 and younger of this site).

The clade [[Ixoliriaceae + Tecophilaeaceae] [Doryanthaceae [Iridaceae [Xeronemataceae [Xanthorrhoeaceae [Amaryllidaceae + Asparagaceae]]]]]] is strongly supported in analyses
using data from four plastid genes (Fay et al. 2000; see also Chase et al. 2000a; Soltis et al. 2007a), but no morphological
characters have yet been found for it. The positions of [Ixoliriaceae + Tecophilaeaceae] and Doryanthaceae are reversed in Kim et al. (2011) and in Fig. 2 in S. Chen et al. (2013), although in Fig. 3 in Chen et al. (2013) the three families form a clade.

Previous Relationships. Dahlgren et al. (1985) took important steps in reorganizing the relationships of "lily-like" monocots. They recognized two groups, Asparagales and Liliales, which were separable by features including patterning of the tepals and absence of phytomelan, both features of their Liliales. However, they still included Iridaceae and Orchidaceae in Liliales.

Age. Crown group Orchidaceae have been dated to ca 111 m.y. (Janssen & Bremer 2004) or (121-)93.7(-75) m.y.a. (Chomicki et al. 2014c). The estimates of Ramírez et al. (2007: calibration by Miocene Goodyerinae pollinaria in amber, see esp. Supplementary Table) are somewhat younger at (90-)84-76(-72) m.y. (recalculated by Gustafsson et al. 2010 - (105-)80(-56) m.y.). Other crown group estimates include (105-)80-77(-56) m.y. (Gustafsson et al. 2010: BEAST), while ages in Bouetard et al. (2010) were slightly older, and the youngest are at around 68 or 51.6 m.y. in S. Chen et al. (2013). Although Janssen and Bremer (2004) did not place Orchidaceae sister to the rest of the order, its stem-group origin was near the beginning of divergence within it, ca 119 m.y.a.

Orchidaceae can be recognised by their strongly
monosymmetric flowers in which the 1-3 stamens are at least basally adnate to
the style. The flowers are usually held upside down because of the twisting of the ovary/pedicel, the median member of the inner whorl then being in the abaxial position and forming the labellum, usually remarkably elaborated. The ovary is inferior and the fruit opens down the sides to release the very numerous and minute seeds.

Apostasioideae have apiculate, carinate tepals, weakly differentiated labellum, and 2-3 stamens that are adnate only to
the base of the style. The other subfamilies have a well developed
labellum and the stamen(s) are more or less completely fused with the style,
forming a gynostemium.

Cypripedioideae have two stamens and a deeply saccate labellum. The other subfamilies
have but a single stamen and the labellum is very variable in shape, although it is not often deeply saccate. Vanilloideae lack both pollinia and viscidia, while both occur in Epidendroideae and Orchidoideae. The former have rather tough leaves and stems and incumbent anthers, the latter often have softer, deciduous leaves and straight anthers.

Evolution.Divergence & Distribution. We know little about the origin and biogeography of the family (see also Chase 2003). Ramírez et al. (2007) suggest that the subfamilies had diverged by the end of the Cretaceous, ca 65 m.y.a., or perhaps slightly later in the early Palaeocene, and that orchid radiation has been a Caenozoic phenomenon; dates suggested by Gustafsson et al. (2010) are somewhat younger, major diversification perhaps occurring during the cooler period at the end of the Eocene and into the Oligocene, rather that during the thermal maximum earlier in the Eocene (c.f. Ramírez et al. 2007).

Despite the minute size of orchid seeds, long distance dispersal seems not to be notably common in Orchidaceae. There are a few exceptions. Thus Bouetard et al. (2010) estimated that crown group Vanilla started to diversify ca 34 m.y.a., at least three instances of long distance dispersal being needed to explain its present distribution. Long distance dispersal seems also to be quite common in Spiranthes, S. romanzoffiana occuring on both sides of the Atlantic, movement having been from west to east (Dueck et al. 2014 and refs).

Gravendeel et al. (2004 and references; see also Peakall 2007) list the numerous hypotheses that have been advanced to explain the diversity of Orchidaceae; these include pollinator specialization, niche partitioning, habitat fragmentation, and wide dispersal of the seeds. Interestingly, there is surprisingly low genetic differentiation between orchid populations, despite the possibility for long-distance transport of the minute seeds with resultant founder effects (Phillips et al. 2012).

Orchid diversity is most often attributed to the nature of the association of the plant with its pollinator, as is discussed below. Normally neither orchids nor pollinating insects are diverse on oceanic islands, but angraecoid orchids are surprisingly diverse on the Mascarene islands, and Réunion in particular also has a diverse insect fauna (Micheneau et al. 2008). In the iconic Mediterranean Ophrys, rapid diversification accompanied shifts to different pollinators, from wasps to apid or andrenid bees (Breitkopf et al. 2015).

Endress (2011a) thought that the inferior ovary in Asparagales might be a key innovation, although where this feature should be placed on the tree is unclear - perhaps here is one place. The presence of pollinia is another feature that he mentioned; this is probably best placed as a synapomorphy of the [Orchidoideae + Epidendroideae] clade.

Some of the distinctive features of the family seem to be biologically connected. Thus pollinia ensure the fertilization of numerous ovules; the minute seeds that result are usually devoid of endosperm or differentiated embryo, and the obligate myco-heterotrophy of the young plant may compensate for the absence of seed reserves (Johnson & Edwards 2000 in part; Eriksson & Kainulainen 2011).

Complicating any simple story about diversification, Orchidaceae are sister to the rest of Asparagales, florally and vegetatively very diverse and with some 6,850 species (c.f. Sargent 2004: Orchidaceae compared with Hypoxidaceae - only 100-220 species). By some measures Asparagales minus Orchidaceae could be considered vegetatively and even florally more diverse than Orchidaceae, although it is hard to compare morphological diversity; Burleigh et al. (2006) suggest that by some measures Orchidaceae do show a notable shift in complexity. However, much floral variation in Orchidaceae is at one level a series of intricate combinations of a rather limited theme. Most species have a single anther, a labellum, a very similar gynoecium, etc., although the variations of the pollinaria and particularly the protean elaborations of the labellum are truly remarkable. Within Orchidaceae, clades of 16, 180, and 130 species are successively sister to the rest of the family, so suggesting a rather more complicated story (see also in part Smith et al. 2011). Indeed, shifts to the epiphytic habit and the associated adoption of CAM photosynthesis are as likely to have been important in orchid diversification as anything else (Gravendeel et al. 2004). Finally, Asparagales as a whole, with around 29,000 species, are sister to commelinids, with some 22,750 species.

Ecology & Physiology.

Fungi and Orchids.

The obligate association of orchids with saprotrophic fungi is central to understanding the physiology of the orchid plant. The fungal hyphae form intracellular pelotons, complex coils of hyphae, inside the plant cells, and these may be digested by the host; the consensus is that orchid mycorrhizae are basically modified ectomycorrhizae (ECM: Smith & Read 1997). Establishment of this association is integral to the successful establishment of the seedling, and the sometimes rather protracted obligate myco-heterotrophic phase of the young plant, where the fungus-plant association does not appear to be antagonistic, compensates for the absence of reserves in the minute seeds (Johnson & Edwards 2000 in part; Eriksson & Kainulainen 2011; Leake & Cameron 2012; Perotto et al. 2014; Rasmussen & Rasmussen 2014). A few orchids can germinate in the absence of a fungus, and in vitro germination of several terrestrial Australian orchids could be as effective on variously doctored asymbiotic media as on the standard symbiotic medium (Bustam et al. 2014). The initial plant-fungal association results in the formation of a protocorm (Peterson et al. 1998) which may have a very distinctive morphology; although it lacks roots, it can have tufts of root hairs (Weber 1981; Bustam et al. 2014).

Which came first, the dust seeds or the myco-heterotrophic association, is almost a chicken-or-egg question, although Rasmussen and Rasmussen (2014) suggest that a developing association with ECM fungi was the spur. A variety of fungi, including the form genus Rhizoctonia which is itself the anamorph stage of several quite unrelated fungi, form the intial fungus-orchid association, later on, specificity may be higher (Rasmussen & Rasmussen 2014), and van der Heijden et al. (2015) estimate that around 25,000 species of fungi are involved, which opens up all sortsof possibilities. Sugars and nitrogen move from the fungus to the orchid (Zimmer et al. 2007; Kuga et al. 2014), indeed, unlike ectomycorrhizal fungi, orchid fungi can break down cellulose, and nutrients moving into the orchid come from the saprotrophic activities of the fungus (Dearnaley et al. 2012; Kohler et al. 2015).

Details of the fungus-orchid association were until recently unclear in Apostasioideae, although it was known that the ECM fungus Tulasnella was involved, a genus also found in Cypripedium, etc. (Kristiansen et al. 2004; see also Yukawa et al. 2009; Roche et al. 2010). The fungus is found in stomatiferous root tubercules, and these may make the plant better able to deal with wet conditions (Stern & Warcup 1994). Interestingly, seeds of Apostasioideae are rather larger than those of other orchids.

Most adult orchids are autotropic, fixing all their own carbon, others are mixotropic, obtaining some carbon from the fungus (or the fungus may obtain carbon from the orchid), while myco-heterotrophic orchids lack chlorophyll and are dependent on the fungus for all carbon (and nitrogen); for a review, see Dearnalay et al. (2012), also Girlanda et al. (2011; Perotto et al. 2014). More or less echlorophyllous myco-heterotrophs (holomycotrophs), have evolved some 30 or more times in Orchidaceae, and some 210 species are myco-heterotrophic (Molvray et al. 2000; Merckx & Freudenstein 2010; Freudenstein & Barrett 2010). They are most common in ground-dwelling Epidendroideae, where about 1 in 10 species is a myco-heterotroph (Freudenstein & Barrett 2010). The Australian Rhizanthella (Orchidoideae-Diuridae) is a subterranean holomycotroph, the flowers even opening underground, but there is still a core group of functioning genes in its choroplast genome (Delannoy et al. 2011).

ECM Tulasnella is a saprotrophic fungus, and although associated with a number of adult orchids, these are autotrophic (Summer et al. 2012; Ogura-Tsujita et al. 2012). In Cymbidium (Epidendroideae) the evolution of mixotrophy and then myco-heterotrophy was associated with the establishment of associations between the orchids and ECM fungi (Ogura-Tsujita et al. 2012). In Corallorhiza (Epidendroideae) several species of Russula form both an ECM association with adjacent trees and an endomycorrhizal association with the orchid (Taylor & Bruns 1999) and the tree is the ultimate source of the carbon. Indirect associations with trees are known from other than myco-heterotrophs (e.g. Bidartondo & Read 2008); see also Bidartondo et al. (2004) for what they call partial mycoheterotrophy. Bi- or unidirectional movement of carbon and nitrogen has been detected in chlorophyllous orchids (e.g. Bidartondo et al. 2004; Cameron et al. 2008; Hynson et al. 2009a). Non-mycorrhizal but lignin-decaying fungi like Mycena (Mycenaceae) are also involved in such associations; Mycena supports the fully myco-heterotrophic Gastrodia confusa in the manner to which it has become accustomed (Ogura-Tsujita et al. 2009: see references for more examples).

Any connection of the specificity of the mycorrhizal association with the diversification of the family in unclear (Otero & Flanagan 2006). The relationship between fungus and orchid is certainly not one-on-one (e.g. Martos et al. 2012: identification method important; Leake & Cameron 2012; Jacquemyn et al. 2013) and can even seem pretty random, at least in the pezizalean associates of Epipactis studied by Tesitelova et al. (2012). Individual North American clades in the myco-heterotroph Corallorhiza striata complex (Epidendroideae-Maxillarieae) are associated with different sets of the fungus Tomentella (Thelephoraceae: Barrett et al. 2010), and Bidartondo et al. (2004) discussed potential host specifity in several European orchids. Roche et al. (2010) studied the specificity of the basidiomycete Tulasnella-Chiloglottis association (see also Otero et al. 2011: Pterostylinae). Nurfadilah et al. (2013) found that fungi varied in their ability to utilize nutrients in phosphorus-poor West Australian soils, suggesting that this might help explain the commonness of different species of orchids there. Indeed, there may be differentiation of fungal communities on different species of orchids that may contribute to niche partitioning (McCormick & Jacquemyn 2013; Jacquemyn et al. 2013 and references).

The Epiphytic Habitat.

Epiphytes are particularly common in Orchidaceae-Epidendroideae. About 70% of all Orchidaceae, some 18,800 species, are epiphytes, and there are more species of epiphytic orchids than of all other vascular epiphytes combined, orchids comprising ca 70% of epiphytic flowering plants (Benzing 1983; Zotz 2013). Speciation in Orchidaceae may increase in epiphytic clades, e.g. in Epidendroideae-Bulbophyllinae (Gravendeel et al. 2004); Chomicki et al. (2014c) estimated that the epiphytic habit had been acquired four to seven times and subsequently been lost rather more often. Epiphytic orchids often have very thick roots and root hairs seem primarily to be for anchoring the plant to the twig (See Siegel 2015 for a readable account of orchid roots).

In the epiphytic habitat orchids have to deal with periodic drought and lack of nutrients (Gravendeel et al. 2004, see also Motomura et al. 2008), rather as in dry terrestrial habitats. Succulence is appropriate for a habitat in which water availability is uncertain (see also Figueroa et al. 2008); terrestrial orchids have thinner leaves. Nyffeler and Eggli (2010b) estimate that some 50+ genera and 2,200 species, especially epiphytic species - or perhaps double that number - are succulents. It is not surprising that many epiphytic Epidendroideae, perhaps some 7,000 species, are likely to have crassulacean acid metabolism (CAM) photosynthesis (Winter & Smith 1996b); variants of CAM photosynthesis such as CAM-cycling are also common (see Cameron et al. 2008 for Oncidiinae). (The actual number of taxa involved is unclear. In a survey of 1,002 Costa Rican orchids, only some 10% of Vanilloideae and Epidendroideae were found to show signs of strong CAM, perhaps 30% more had weak CAM; CAM was not found in Orchidoideae and Cypripedioideae [Silvera et al. 2010a].) Studies on cauline pseudobulbs, common in epiphytic orchids, suggest that they may sometimes carry out CAM even although they lack stomata. CAM occurs in Bulbophyllum minutissimum, however, the pseudobulb there is a modified leaf, even if lacks a blade, so one presumes there are stomata (Kerbauy et al. 2012 and references). CAM has evolved perhaps ten times in Orchidaceae, it has also reversed to C3 photosynthesis, and there are intermediates; adoption of CAM is predominantly by epiphytic Epidendroideae growing at low altitudes and drier conditions (Silvera et al. 2009; Kerbauy et al. 2012) and has been linked to the Caenozoic radiation of that subfamily (Silvera et al. 2009). Gene duplication has been implicated in the functional diversification of genes like phosphoenolcarboxylase involved in CAM photosynthesis (Silvera et al. 2014).

Another problem faced by epiphytic plants is damage to tissues caused by UV-B radiation. Twig epiphytes in particular, concentrated in a clade of the New World Epidendroideae-Cymbidieae-Oncidiinae, face such problems. They grow on twigs less than 2.5 cm in diameter and in very exposed and high light conditions. Recent work suggests that chalcone synthase genes can be induced by UV-B light in the root tips of epiphytic orchids, and as a result UV-B-absorbing flavanoids are synthesised (Chomicki et al. 2014c: for sunlight and epiphytism, see also Bromeliaceae). A leafless orchid was included in the UV-B study by Chomicki et al. (2014c), and it showed similar behaviour to the two leafy epiphytic taxa in the study.

The leaves of some epiphytic Epidendroideae-Vandeae may not be photosynthetic and/or are soon deciduous. The vegetative plant then consists largely of photosynthetic roots. These roots may be stout (ca 5 mm across) and terete, as in Dendrophylax, while the roots of the aptly named Taeniophyllum are distinctively flattened (e.g. Carlsward et al. 2006b). There are over 200 species ofleafless Epidendroideae, all epiphytes, with an estimated 20 or morwe independent losses of leaves (Freudenstein 2012). How carbon dioxide and water flux are controlled in leafless epiphytes is unclear, especially because there are no stomata (?never) in the roots, although the aeration units may be stomata analogues (Benzing et al. 1983; Cockburn et al. 1985). Roots of leafless orchids like Campylocentrum tyrridion, which lack stomata, also carry out CAM (Kerbauy et al. 2012). The photosynthetic pathway in root and leaf may be different, the former being C3 while the latter is CAM (Martin et al. 2010), indeed, photosynthesis in orchid roots is poorly understood.

Twig epiphytes of the Oncidiinae are particularly distinctive. They grow on twigs less than 2.5 cm in diameter and their seed coats have little grapnels, perhaps aiding in their attachment to the twigs (Chase & Pippen 1988). The plants are very small and may mature within a year (Chase 1987; Chase and Palmer 1997; Neubig et al. 2012a); indeed, many of these epiphytes are exposed to light immediately on germination, rather than starting off with a slow-growing subterranean mycotrophic phase (Leake & Cameron 2012). Their leaves are isobifacial and are arranged like a small fan (the psygmoid habit) and the plants have no pseudobulbs. All in all, they look like very young plants of other Oncidiinae and are more or less paedomorphic (Chase 1987; Neubig et al. 2012a for references; Chase et al. 2005 for genome size).

Mycorrhizal associations are less common in epiphytic plants (e.g. Janos 1993; Desirò et al. 2013). However, Sebacinales and Tulasnellales have been found as ectomycorrhizal associates in neotropical epiphytic orchids, species of Tulasnellales, at least, colonizing more than one species of orchid (Kottke et al. 2008; see also Martos et al. 2012; Gowland et al. 2013). Basidiomycete fungi are to be found in the photosynthetic roots of the leafless epiphyte Dendrophylax lindenii (Chomicki et al. 2014b).

Pollination Biology & Seed Dispersal.

Pollination Biology.

Orchid flowers may be notably long-lived (months), although some last only for a single day. Flowers are commonly resupinate, the ovary being twisted about 180°, the labellum ending up in the abaxial position (Ernst & Arditti 1994; Yam et al. 2009 for reviews). However, the amount of resupination often varies within a plant when the inflorescence is arching; all flowers of the inflorescence are oriented so that their labellum is in the same position with respect to gravity, with the ovary sometimes being twisted 360° (as in Angraecum, etc.) or not at all. Catasetum has resupinate staminate flowers, but the carpellate flowers are not resupinate (see below). Fischer et al. (2007) discuss the variety of ways - of which twisting of the pedicel is but one of the mechanisms involved - that flowers in the speciose Bulbophyllum present themselves in the Malagasy region. In genera like Calopogon the flowers are never resupinate, and all flowers on the erect inflorescence show "normal" monocot orientation, the labellum being adaxial.

The most conspicuous element of floral variation is the labellum, a highly-differentiated member of the inner whorl of tepals, which shows a truly remarkable diversity of form and colour (Rudall & Bateman 2002; see also 2004); duplication of genes may be involved (Mondragón-Palomino & Theißen 2008). The spatial relationships of the labellum and column in particular force the pollinator to approach the flower in a particular way, and in general, pollinaria are very precisely placed on the pollinator, closely related orchid species differing in exactly where their pollinaria are placed (e.g. Maad & Nilsson 2004). After the pollinarium is attached, the pollinia may move, so bringing them into the proper position for pollination (for pollinia and polinaria, see Rasmussen 1982; Freudenstein & Rasmussen 1996, 1997; Johnson and Edwards 2000; Pacini & Hesse 2002; Freudenstein et al. 2002; Selbyana 29: 1-86. 2008).

A final distinctive feature of many orchid flowers is that the ovules are usually not fully developed - and may not even be recognizable - at anthesis, and fertilization is often delayed relative to pollination, as in Cypripedium. The time between pollination and fertilization ranges from four days to ten months (in Vanda), the normal time being one week to six months (Wirth & Withner 1959, Yeung & Law 1997; also Sogo & Tobe 2005, 2006d for references: ?Apostasioideae). Even after fertilization, it may be a month before embryo development begins, as in Sarcanthinae (Wirth & Withner 1959 for references).

In the following brief discussion on orchid pollination, I emphasize first rewards, then the pollinator, with some other issues mentioned at the end. For pollination, see also van der Pijl and Dodson (1966).

Rewards - or Lack Thereof.

The plesiomorphic condition for the family may be to lack nectar (Jersáková et al. 2006); all told, perhaps 8,000 or more species of orchids lack nectar. Cozzolino and Widmer (2005; see also Schiestl 2005) suggested that orchid diversification is associated with the deceptive pollination mechanisms that are so prevalent in the family; about one third of the species - estimates range from 6,500 to 10,000 - are pollinated in this way (Schiestl 2005, 2010 for reviews, the latter brief; Schlüter & Schiestl 2008: molecular mechanisms; Peakall 2009: deceit and speciation; Schaefer & Ruxton 2010: exploitation of perceptual biases of the pollinator by the plant; Gaskett 2011: the pollinator's point of view in sexual deception; Xu et al. 2012; Pinheiro & Cozzolino 2013: deceit in the large genus Epidendrum). Deceit comes in various guises, from sexual deceit, where the orchid mimics a female insect and pollen exchange occurs during pseudocopulation (e.g. Ophrys below) to domicile deceit, as in species of Serapias (Orchideae: Bellusci et al. 2008 for a phylogeny) and Cypripedium (Cypripedoideae: Pemberton 2013) that attract pollinators by mimicking a nest hole.

Flowers of the European Ophrys (Orchidoideae-Orchideae) are well known for deceit pollination, their labellum mimicking female bees and wasps (e.g. Kullenberg 1961; Paulus 2006). They also produce chemicals that are very similar to insect pheromones; alkenes (hydrocarbons with at least one double bond) are part of the chemical component of this mimicry (e.g. Stökl et al. 2009; Ayasse et al. 2011; Xu et al. 2012). Morphology and scent together enable the Ophrys flower to mimic female insects (Cortis et al. 2009 and references), pollination occurring as male bees and wasps in particular attempt to copulate with the flowers (Kullenberg 1961). Barriers to crossing - floral form and scent again - act before pollination; no deleterious effects of hybridization, which occurs in the wild, have been noted (Xu et al. 2011). Scent chemicals are common in related genera as well (Schiestl & Cozzolino 2008), and Ophrys is part of a larger clade in which food deception seems to be the basic condition (Inda et al. 2012). However, there is currently much discussion about species limits in Ophrys, with estimates of species numbers ranging from 16 to 252 species (Bateman et al. 2006a, 2011a; Devey et al. 2008; Bradshaw et al. 2010; Vereecken et al. 2011; Delforge 2006 for photographs of the species). Paulus (2006: p. 315) thought that "species formation in Ophrys always proceeds with the aquisition of a new species of pollinating males", and species that had different pollinators might show "genic rather than genome-wide differences", speciation had barely begun (Sedeek et al. 2014: p. 6202). For diversification in Ophrys, which is a Pleistocene phenomenon, see Breitkopf et al. (2015).

In the Australian Chiloglottis (Orchidoideae-Diuridae) there is a fair degree of congruence between the phylogenies of the orchids and the deceived wasps (Mant et al. 2002, 2005; see also Weston et al. 2011; Miller & Clements 2014). Again, understanding species limits is critical; here there seem to be a number of cryptic species (Griffiths et al. 2011). Caladenia (also Diuridae) is another example (Jones et al. 2001). In such sexually-deceptive orchids both morphological and genetic differences between species or even genera are slight (Schiesl 2005 and references; Mant et al. 2005; see also below) and post-pollination barriers may be nonexistent (Whitehead & Peakall 2014).

In the New World, pollination during pseudocopulation with fungus gnats (dipterans, often Sciaridae) has been reported in the large genus Lepanthes (Blanco & Barboza 2005). How this system might function is unclear since there is no obvious connection between the morphology of the orchid flower and that of the fungus gnat (Singer 2011).

Chemical signalling between plant and insect to effect pollination occurs in many situations, not only enhancing floral mimicry in pseudocopulation. Thus wasps may be attracted to orchid flowers that produce chemicals similar to those produced by damaged plant tissue - the wasps visite the flower expecting to find caterpillars, but pollination occurs instead. Similarly, Dendrobium sinense, pollinated by a hornet, has a floral bouquet that includes the same chemicals as in the alarm pheromones of Apis, which the hornet commonly catches (Brodmann et al. 2009).

Food deceit is quite common, as with pollen mimicry in Vanilloideae-Pogonieae where it characterises a clade that includes temperate species; pollen is apparently available for removal (Pansarin et al. 2012). A number of species of Epidendroideae-Oncidiinae have flowers like those of oil-producing Malpighiaceae. They have radiating, clawed, yellow or purple "petals" that are similar in both shape and in colour, bee-UV-green, to flowers of Malpighiaceae, and they may be part of a Batesian mimicry system, both groups being visited by bees like Centris, etc.. The orchids often have no reward for the bee (Neubig et al. 2012a; esp. Papadopulos et al. 2013), although some do have rewards (see below). The mimicry unit of the orchid is formed largely by the labellum, the column being equivalent to the banner petal of a malpighiaceous flower. M. P. Powell (in Neubig et al. 2012a) has estimated that such mimicry may have evolved at least 14 times within Oncidiinae, indeed, it may be both lost and regained (Papadopulos et al. 2013). Some Oncidiinae mimic Calceolaria, another oil flower (Neubig et al. 2012a).

Many orchids do have rewards for the pollinator. Flowers with rewards have frequently been derived from those that do not (Cozzolino et al. 2001; Cozzolino & Widmer 2005; Smithson 2009; Pansarin et al. 2012; Johnson 2013). In the speciose African Disa (Orchidoideae), there have been several transitions from deceit to nectar rewards, and loss of nectar, and independent gains and losses of spurs - all without having much of an effect on diversification rates (Johnson et al. 2003). The production of rewards may also be derived in Vanilloideae-Pogonieae (c.f. Pansarin et al. 2012).

Pollen alone is collected from flowers of Apostasioideae, and even from some Vanilloideae (Pansarin et al. 2012). Nectar flowers are quite common (Bernadello et al. 2007 and references). The flowers of Satyrium are not resupinate and have twin nectar spurs (Johnson et al. 2011a), while Angraecum, Habenaria, etc., also have nectar spurs; epithelium on various tepals may also produce nectar (Davies et al. 2005; Hobbhahn et al. 2013), but nectaries in Orchidaceae are never septal. Hobbhahn et al. (2013) discuss the evolution of nectaries of various types (a secretory nectariferous epidermis is here descibed as being "recapitulatory") with Disa, which happened some eight times there alone. In a number of species of Maxillaria hairs on the labellum contain protein and perhaps also starch and function as pseudopollen, so rewarding the pollinator (Davies et al. 2000; Davies 2009).

Resins and oils are also quite common rewards; for a summary of oil flowers in Orchidaceae, which have evolved probably at least a dozen times, eight times in Maxillarieae alone, see Renner and Schaefer (2010). Orchids with oil as a reward may show convergence with the flowers of other oil-pollinated plants. Some 70 species of Oncidiinae have elaiophores, often on the labellum; these may be epithelial or tufts of secretory hairs (Blanco et al. 2013; Davies et al. 2014 and references) and be visually similar to elaiophores on the calyx of Malpighiaceae, or the flower as a whole may be like those of Malpighiaceae. The distinctive oil secreted is very similar to that produced in the flowers of Malpighiaceae (see above; Reis et al. 2007 and references); some kind of Müllerian mimicry system may be operating here (Papadopulos et al. 2013), but such systems are difficult to categorise from this point of view (see also Policha et al. 2014). Pollination of some South African Orchidoideae-Coryciinae (e.g. Disperis) is by oil-collecting bees; the flowers have paired, pouch- or spur-like structures like those of another local oil plant, Diascia (Scrophulariaceae: Pauw 2006). The South African Huttonaea, perhaps immediately unrelated, also has oil flowers (Steiner 2010); Steiner et al. (2011) analyzed scent composition of many southern African oil-secreting Diseae. Resins as a reward have evolved several times in Maxillaria and its relatives, but other rewards occur there, and there are even some species that have flowers that may mimic the presence of resin rewards (Whitten et al. 2007; Davies & Stpiczynska 2012). See also Chase et al. (2009) and Steiner (2010) for oil flowers.

Pollinators.

Turning now to different pollinator groups, fly pollination is common (Christensen 1994), especially in Epidendroideae, for example in the very speciose and largely Old World Bulbophyllum. Dark, purplish-coloured flowers with carrion scent, a mobile labellum, and often dangling hairs of various kinds attract flies. A number of taxa have sweet, fruity scents and lighter-coloured flowers and are pollinated by fruit flies - which may also be commercially important pests (Tan 2008 and references, see also Texeira et al. 2004; Fischer et al. 2007 for resupination there). In the New World, pollination during pseudocopulation with fungus gnats (dipterans, often Sciaridae) has been reported in the large genus Lepanthes (Blanco & Barboza 2005). How this system might function is unclear since there is no obvious connection between the morphology of the orchid flower and that of the fungus gnat (Singer 2011). Pollination by fungus-visiting drosophilids is also known in Dracula, although other flies are also involved (Policha et al. 2014). Fly pollination of one sort or another, sometimes with with nectar as a reward, but usually because the orchid simulates decay or a fungus (sapro- or mycomyophily), is likely to predominate in the some 4,000+ species of Pleurothallidinae, to which Lepanthes and Dracula belong, and here self incompatability tends to be developed, as in some other Epidendroideae (Borba et al. 2011; Duque-Buitrago et al. 2014). Pollination by Drosophila and Scatophaga is also known in Cypripedium (Li et al. 2012).

Moth, butterfly, and even bird pollination are also well known in the family. Angraecum sesquipedale (Epidendroideae-Vandaeae), from Madagascar, is a classic example of moth pollination. There the spur is about 30 cm long, and the pollinator for long remained unknown, although Darwin (1862) suggested that some moth with a proboscis that long would be found. Indeed, Xanthopus morgani praedicta, with a proboscis length of about 25 cm, was subsequently discovered (Nilsson et al. 1987; Nilsson 1988: Wasserthal 1997; Arditti et al. 2012; Micheneau et al. 2010: pollination in angraecoid orchids in general - there are over 200 species). For spurs, nectariferous and otherwise, in Orchidoideae-Orchidinae, see Bell et al. (2009), and for the great floral and pollinator diversification in some of its genera, including Disa, see Johnson et al. (1998, 2013) and Bytebier et al. (2007). For paired spurs in Satyrium, see Johnson et al. (2011a), and for spurs in the largely Australian Diurideae, see the summary in Weston et al. (2011: also various kinds of mimicry, nectar evolved [and lost] many times, etc.). Spurs are common in Vandaeae; for spurs in Aeridinae, see Topik et al. (2005).

It has been estimated that perhaps 60% of Orchidaceae are pollinated by bees (Schoonhoven et al. 2005), whether deceived or not. Williams (1982) discussed the general importance of male euglossine bees in particular in the pollination of neotropical Epidendroideae (see also Roubik 1988). Male bees pollinate as they search for fragrances that they collect and store in their hind tibial pockets, these fragrances perhaps being involved in pre-mating isolation in the bees (Zimmermann et al. 2009). There are some 190 species of orchid bees and they pollinate perhaps up to 25% of tropical American Orchidaceae, hence their common name, orchid bees. About 700 species of orchids have fragrances that attract male bees, some 85% of all plants with such fragrances (Ramírez 2009). Euglossine pollination in general is especially common in orchids growing at lower altitudes, and anywhere from 700-2,000 species may be so pollinated (Cameron 2004 and references; Zimmermann et al. 2009; Ramírez et al. 2011 - Photo: bee pollinators). Euglossines also pollinate many Zingiberales, Gesneriaceae, Lecythidaceae, etc., which may be visited for nectar, pollen, or resins. For further discussion, see Clade Asymmetries.

Although the bees are effective pollinators, the relationships between orchids and euglossine bees are non-specific on both sides (Cameron 2004). Importantly, crown-group euglossines can be dated to 42-27 m.y.a., with especially rapid diversification 20-15 m.y.a. (Ramírez et al. 2010) or (35-)28(-21) m.y.a. (Cardinal & Danforth 2011). (Stem-group euglossines are Cretaceous in age - e.g. Grimaldi & Engler 2005.) The orchids these bees pollinate speciated abou 12 m.y. later, (31-)27-18(-14) m.y.a (Ramírez et al. 2011: estimates from bee-visited Catasetinae, Zygopetalinae and Stanhopeinae, immediately unrelated clades). At least most of the compounds that the bees pick up from the orchids are usually found elsewhere, and many other fragrances are acquired from other sources. Closely related and sympatric species of Euglossa did show greater disparity in the fragrances they preferred than might be expected; overall, however, the most dominant compounds in the fragrances were highly homoplasious (Zimmermann et al. 2009). Orchids may be exquisitely adapted to individual pollinators whose sensory biases they may exploit (Schiestl 2010; Ramírez et al. 2011), but individual species of orchid bees may pollinate several species of orchids, plant-pollinator relationships being highly nested; furthermore, few of the fragrances sought by male bees are unique to the orchids (Ramírez et al. 2011). Given the timing of evolution of orchids and bees, and the relative dependancy relationships of the two, simple insect-orchid co-speciation, or perhaps coevolution of any kind, is not an explanation for the diversification of the orchids.

The pollination of Catasetinae, Catasetum in particular, by male euglossine bees is well known (Darwin 1862; Chase & Hills 1992 for a phylogeny; Gerlach 2013). Catasetum has remarkable flowers, even for an orchid: Not only may resupination differ between staminate (resupinate) and carpellate (non-resupinate) flowers, but there are many other striking differences, especially in labellum morphology, between the two; indeed, staminate and carpellate specimens were once put in separate genera, Myanthus and Monachanthus respectively. The attachment of the pollinaria on the bees is by a trigger-activated explosive mechanism (Nicholson et al. 2008). The insect is startled, and Romero and Nelson (1986) suggested that as a result the bees subsequently avoided staminate flowers, hence the very different morphologies of the carpellate flowers, which, however, are more similar between the species: "The battered pollinator will remember the negative experience with the staminate flower" (Gerlach 2012: p. 39). The final wrinkle is that the kind of flower produced is determined, at least in part, simply by light; bright light tends to favour the production of carpellate flowers (Gregg 1975).

General.

The connection between the orchid-pollinator relationship and orchid diversification is a matter of active discussion - but see the caveats above about estimating diversification. Reproduction in orchids may often be pollinator-limited (Tremblay et al. 2005), with few flowers on an inflorescence producing seeds, however, the production of huge numbers of seeds by each fruit may compensate for this - as Pérez-Hérnandez et al. (2011) noted, orchids "specialize in chance". Recent studies suggest that when pollinators visit orchid flowers in the course of deceptive pollination or to pick up scent rewards - specialized pollination mechanisms - pollinator specificity is greater and species richness is greater than when pollinators visit for nectar (Schiestl & Schlüter 2009; Xu et al. 2011; Schiestl 2012: sister-group comparisons; see also Dressler 1968; Scopece et al. 2010a for pollination efficiency). Thus deceit pollination may under certain situations increase outcrossing and speciation, the latter perhaps because of the specificity of the pheromones produced by the plants (Jersáková et al. 2006; see also Ledford 2007). Self-pollination can be quite common in Madagascan Bulbophyllum.

The presence of well-developed and effective premating barriers in Orchidaceae may have obviated any pressure for the selection of postmating barriers (e.g. Whitehead & Peakall 2014). As a result, artificial crosses are often easy to make, and hybrids may have three or more genera in their parentage, although how these will look when generic boundaries are redrawn is unclear. Thus many genera in Laeliinae can be crossed artificially (van den Berg et al. 2000, 2009). In European orchids, at least, with generalized food-deceptive mating mechanisms, barriers to crossing may be postzygotic, whereas those that practice sexual deception have prezygotic reproductive barriers, and introgression is more likely in this latter situation (Cozzolino & Scopece 2008).

Selfing in orchids may be quite common (Gamisch et al. 2014 for a review). The bee-mimic Ophrys apifera may self if not visited by bees; there the pollinia curve downwards and meet the stigma. In Madagascan Bulbophyllum selfing varies infraspecifically and it is associated with the loss of the rostellum, as it often is elsewhere in the family (Gamisch et al. 2014; see also e.g. Peter & Johnson 2009). There are other mechanisms, too, as in Paphiopedium parishii where the contents of the anther liquefy and slop on to the stigma (L.-J. Chen et al. 2013).

Tremblay et al. (2005) reviewed the evolutionary consequences of the diversity of the pollination mechanisms of Orchidaceae and the remarkable variation shown by their flowers. Orchid diversification is often explained in terms of the close association between pollinators and individual species of orchids, but recent work suggests very strongly that strict co-speciation should not always be assumed (Ramírez et al. 2011), and factors other than floral variation may have contributed to the diversification of Orchidaceae - see "Vegetative Variation" and "Ecology & Physiology" above. Although pollination relationships in orchids are usually thought of as being very precise, with close pollinator-plant associations, a single species of Epipactis may be visited by over 100 species of pollinators (Tremblay 1992: Cypripedioideae in general a bit promiscuous?), while in some areas, at least, pollinator specificity, although greater than in Ranunculaceae, is less that in Polemoniaceae (Waser et al. 1996). The generation of diversity by floral specialization may be relatively uncommon in flowering plants in general, although perhaps occurring here (Armbruster & Muchhala 2009).

For summaries of pollination in Orchidaceae, see van der Cingel (1995, 2001), Endress (1994b), Biol. J. Linnean Soc. 173: 713-773. 2013, etc. - and of course the classic study by Darwin (1862a) is still worth reading (see also Yam et al. 2009). For a general discussion on floral evolution in the family, with an emphasis on terata and homeosis s.l., see Rudall and Bateman (2002); Rudall and Bateman (2004: outgroup a Hypoxis-type flowers, but of no consequence) emphasize the various processes involved.

Seed Dispersal.

The minute dust seeds of most orchids are a distinctive feature of the family (e.g. Moles et al. 2005a, and these are often produced in huge numbers, up to 4,000,000 seeds per fruit or 74,000,000 seeds per plant, the seeds being as little as 150 µm long or less (Arditti & Ghani 2000; Yam et al. 2009). Orchidaceae have particularly small seeds when compared with their immediate relatives (Moles et al. 2005a), and the seeds usually lack endosperm and a differentiated embryo. Much of the seed, small as it is, is in fact empty space, and the seeds are well suited for wind dispersal (Arditti & Ghani 2000); the trichomes on the endocarp quite commonly found in Orchidaceae may function as elaters aiding in seed dispersal (Kodahl et al. 2015). Although Arditti (1967) did suggest that a few species had recognizable cotyledons, the species mentioned are not basal in the tree. The subterrananean myco-heterotroph Rhizanthella has baccate fruits with large, crustose seeds (Weston et al. 2011). In Vanilla imperialis a white foamy substance exudes from the fruit, carrying the seeds along with it (Kodahl et al. 2015 - note the variation in seed morphology in Vanilloideae), indeed, Rodolphe et al. (2011) suggest that seeds in Vanilla may sometimes be dispersed by euglossine bees.

Plant-Animal Interactions.

Members of Orchidaceae are not often eaten by caterpillars (Janz & Nylin 1998) or by insect herbivores in general, although Riodininae-Riodininae larvae may be found on them (Hall 2003 and references).

Bacterial/Fungal Associations. Orchids characteristically have a very close association between basidiomycete and some ascomycete fungi. Rhizoctonia (= Ceratobasidium) is a common anamorph or form genus that encompasses a multitude of sins (Dearnalay et al. 2012) - Russulaceae, Tuber, and Sebacinales-B (found with autotrophic orchids, and in the same clade, but different from Sebacinales-B on Ericaceae - Setaro et al. 2012) and -A (with mixotrophic and myco-heterotrophic orchids) are all involved. The commonest families are Tulasnellaceae (perhaps the most important group - Martos et al. 2012), Ceratobasidiaceae and Sebacinaceae (see Currah et al. 1997 and Yukawa et al. 2009 for lists of fungi; Otero et al. 2002; Roy & Selosse 2009; Weiß et al. 2009), but some neotropical Epidendroideae have Atractiellomycetes (in the same clade as Puccinia) as mycobionts (Kottke et al. 2010). The fungi associated with the plant as it germinates may be quite different from those associated with the adult plant (Hashimoto et al. 2012 and refs.). Although Rinaldi et al. (2008) thought that only 10 species of fungi might be involved, the number is far greater, even on a single species and in relatively small areas (e.g. Martos et al. 2012; Jacquemyn et al. 2013), and van der Heijden et al. (2015) estimated that about 25,000 species of basidiomycetes are involved, as many as in the mycorrhizal associations of all other embryophyte combined. Martos et al. (2012) discussed the literature on the phylogenetic signal of orchid and fungus.

Yukawa et al. (2009) suggested that the basidiomycete Cantherellales may have been the fungus group first associated with Orchidaceae. At least some of the fungi are probably saprophytes living on decaying plant material that can also form close relationships with orchids (Ogura-Tsujita et al. 2009; Yukawa et al. 2009).

Recent work on orchids growing on Réunion suggests that the nature of the mycorrhizal network in epiphytic and terrestrial species differs, with only 10 of the 95 fungal species (taxonomic units) recorded found in species from both groups. Furthermore, most of the species obligately restricted to one of the groups as well those occuring in both were found on only one or two of the orchid species (Martos et al. 2012). Differences between the species of fungi found in the two habitats, or in features of the orchids that affect colonization by the fungi, may both explain this striking pattern (Leake & Cameron 2012). Chomicki et al. (2014b) discussed the association of the "leafless" epiphyte Dendrophylax with endomycorrhizal fungi.

For endophytic fungi, see Bayman and Otero (2006). Very little is known about them, and the one fungus may even be pathogen, endophyte, and mycorrhizal symbiont.

Vegetative Variation. Orchidaceae show considerable diversity in habit and other vegetative features despite their generally modest size. However, some Sobralieae are slender, cane-like plants up to about 10 m tall and viny Vanilloideae, even including the myco-heterotrophic Galeola, may be several metres long. The geophytic habit is quite common in Orchidoideae in particular. Tatarenko (2007) summarized the extensive vegetative variation of temperate orchids, i.e. especially Orchidoideae.

The vernation of orchid leaves varies. The blade may be quite thin to thick, bifacial, isobifacial or unifacial (terete), and the leaf bases are sometimes massively swollen. Leaves may be spirally arranged to 2-ranked, and sometimes articulated with the sheathing base. Some ground- and shade-dwelling species have distinctively-coloured and -patterned leaves that makes them particularly attractive to horticulturists. Extrafloral nectaries are scattered, being found on the stems opposite the leaves in Vanilla, at the bases of the pedicels in Cymbidium, etc.

Stems, leaves or even roots may be succulent (Nyffeler and Eggli 2010b; also Figueroa et al. 2008). Individual leaf blades of Bulbophyllum may be some and weigh. The roots of mature plants of "leafless" Epidendroideae-Vandeae and those of many other Epidendroideae appear to lack root hairs, although they may develop on the side of the root facing the substrate (von Guttenberg 1968; Pridgeon 1987); the root hairs ("rhizoids") are sometimes described as being branched (Rasmussen 1999). Orchid roots are often rather stout; a velamen, made up of dead cells with spiral thickenings on the cell walls, is well developed around the outside (von Guttenberg 1968; see below). Pneumathodes are common in Epidendroideae, and leafless Vandeae have aeration units in their roots. These latter consist of distinctive exodermal cells, a space beneath, and a pair of thin-walled cortical cells; such aeration units are also found in related leafy Vandeae (Benzing et al. 1983; Carlsward et al. 2006a, b). Roots of New World epiphytic Epidendroideae in particular have distinctive tilosomes, cells of the innermost layer of the velamen that are adjacent to the passage cells of the exodermis and that have complex often lignified excrescences developing from the wall (Pridgeon 1987; Pridgeon et al. 1983). However, such cells are also found in ground-dwelling Orchidoideae-Spiranthinae (Figueroa et al. 2008) and their exact function is unclear.

The End. We can now return to the question, Why are there so many orchids? Orchidaceae are distinctive in several ways, of which their flowers and fruits are just two. Vegetative and physiological variation, more or less associated with habit and habitat, is almost equally striking. Futhermore, Waterman et al. (2011) distinguish between speciation and coexistence in orchids, and note that shifts in details of pollination (placement of pollinaria, pollinating insect) occur with speciation, although associations with different fungi may promote the co-occurrence of immediately unrelated orchid species. No one feature of itself is likely to be responsible for orchid diversification.

Genes & Genomes. There is much variation in chromosome number and size. Thus Apostasioideae and Orchidoideae have small chromosomes, while larger chromosomes occur in Cypripedioideae and Vanilloideae; Felix and Guerra (2010) survey chromosome number variation in Epidendroideae. For genome size, see Leitch et al. (2009) and Jersáková et al. (2013); it varies 168-fold.

The subterranean holomycotroph Rhizanthella (Orchidoideae-Diuridae) has a very small plastid genome, about 59,000 BP, but there is still a core group of functioning genes (Delannoy et al. 2011), and over two dozen functional gene were found in the still smaller genomes of Epipogium, to 19 kbp (E. roseum), which particular genes remaining functional depending on which essential genes had moved to the nucleus, etc. (Schelkunov et al. 2015). Barrett et al. (2014a, esp. b) discuss how the plastome has degraded in Corallorhiza. All members have at least some chlorophyll, but the amount of the plastome retained is about inversely proportional to how much photosynthesis going on in the plant.

matK in Apostasioideae may be in transition from a possibly functional gene to a pseudogene; in the Orchidaceae examined (but the sampling is poor) it is a pseudogene (Kocyan et al. 2004).

Chemistry, Morphology, etc. Pyrrolizidine alkaloids are known from genera like Phalaenopsis and Pleurothallis.

For the velamen and its systematic significance, see Porembski and Barthlott (1988) and Pridgeon (1987). Note that there is some doubt as to whether or not Apostasioideae have a velamen; I follow Pridgeon (1987). Furthermore, Porembski and Barthlott (1988) noted that all Apostasioideae, also a number of Orchidoideae, Cypripedioideae, etc., had a rhizodermis, but Pridgeon (1987) scored only the single Apostasioideae he examined and no other orchid as having a simple epidermis; one might have thought that a rhizodermis and a simple epidermis were the same thing... Orchidaceae are one of the few non-commelinid clades with SiO2 bodies (e.g. Prychid et al. 2003b); they show some variation in form and are sometimes lost (Freudenstein & Rasmussen 1999).

Cardoso-Gustavson et al. (2014) discuss the occurrence of often mucilage-secreting bicellular hairs ("colleters") in the flowers of Epidendroideae. They note that these may be on the outside of the flower, and suggest they may be connected with the extrafloral nectaries that are also found on the inflorescences of some Epidendroideae.

Monosymmetry of the flower in many, but not all orchids - and in Hypoxidaceae and Doryanthaceae - is evident even in the earliest primordia (Kurzweil & Kocyan 2002 and references). A few Orchidaceae have more or less polysymmetric flowers, and in Telipogon (Epidendroideae - Oncidiineae) a polysymmetric perianth becomes evident only late in development (Pabón-Mora & González 2008). Duttke et al. (2012) discuss the remarkable terata to be found in Neofinetia falcata (Vandeae: Aeridinae) that have been accumulated in Japan over the last 350 years. For floral development and the expression of B-, C- and D-class genes in particular in Dendrobium, see Y. Xu et al. (2006); genes of all three classes are expressed in the column. The sequence of organ initiation varies considerably within the family (Pabón-Mora & González 2008). Thus Apostasioideae and Cypripedioideae have simultaneous initiation of members of the inner tepal whorl, the plesiomorphic condition for Asparagales (Kocyan & Endress 2001a); have Vanilloideae been studied? At least some Orchidaceae have placentoids (Weberling 1989).

Anthers of some species appear to be bisporangiate in early development (Freudenstein & Rasmussen 1996). Prutch and Schill (2000) discuss variation in the morphology and ultrastructure of the stigma; variation seems to be at about the subfamilial level. Kodahl et al. (2015) discuss embryo sac formation (6-nucleate embryo sacs are common in the family), double fertilization (extent unclear) and endosperm development (or lack thereof); see also Swamy (1949) and Wirth and Withner (1959). Although the seeds are generally minute and the testa cells have thin walls, Selenipedium (Cypripedioideae) has a hard,
dark testa, although apparently it lacks phytomelan.

Phylogeny. Cameron (2007) provided a summary of phylogenetic studies on the family. There may still be some uncertainty over
the position of Cypripedioideae (e.g. Cameron 2004). In some analyses they grouped (albeit weakly) with Vanilloideae (Freudenstein & Chase 2001) or were sister to Orchidaceae minus Apostasioideae, which might make sense if thinking about androecial evolution (alone Cameron et al. 1999: one gene, successive weighting). However, they are often placed sister to Orchidaceae minus Apostasioideae and Vanilloideae (e.g. Kocyan et al. 2004; Cameron & Chase 2000; Cameron 2002, 2005b, 2006: two genes, in a basal trichotomy with atp alone; Górniak et al. 2010: nuclear gene Xdh). This latter hypothesis, followed here, suggests that the monandrous condition may have evolved twice (see also Freudenstein et al. 2002, 2004). There are also suggestions that Codonorchis is sister to [Epidendroideae + Orchidoideae] (e.g. Clements et al. 2002) or basal in Orchidoideae (Cameron 2006). It may need to be kept separate if in the former position (it has whorled leaves - see Cameron 2006; c.f. Jones et al. 2002).

For relationships in Cypripedioideae, including also a morphological survey, see Albert (1994). Li et al. (2011) found morphology sometimes to have misled over relationships in Cypripedium; for a phylogeny of Paphiopedilum, see Chochai et al. (2012).

Orchidoideae include the erstwhile Spiranthoideae which have incumbent anthers (as in Epidendroideae) with apical rostellar tisssue. Relationships within Orchidoideae are becoming fairly well resolved (e.g. Cameron 2004); see also Inda et al. (2010: cox1 intron). For relationships in Orchideae, see Inda et al. (2012). In Asia, Habenaria is diphyletic and Platanthera triphyletic (Jin et al. 2014: relationsips of Orchidinae and Habenariinae); New World species of Habenaria are monophyletic, although sectional limits need revision (Batista et al. 2013; Pedron et al. 2014). Clemens et al. (2002; see also Miller & Clements 2014; Weston et al. 2014) clarify relationships of Diuridae, a few of which are to be placed in Epidendroideae; for Codonorchis, see above. Disa is especially diverse in the Cape Region (see Bytebeier et al. 2007, 2008); for a phylogeny of Satyrium, see van der Niet and Linder (2008); it has diversified in the Fynbos region (Verboom et al. 2009). Prescottiinae s.l. have diversified at very high altitudes - up to 4,900 m - in the Andes (Álvarez-Molina & Cameron 2009). For information about relationships in the speciose Caladenia, see Australian J. Bot. 57(4). 2009, for a study of Diuridae, Clements et al. (2002), of Pterostylis and relatives, see Clements et al. (2011), of the African Disa (Disinae), see Bytebier et al. (2007), and of the American Chloraeinae, see Cisternas et al. (2012). For the phylogeny of Cranichidae, see Salazar et al. (2003: monophyly and characters of subtribes, 2011a: comments on Spiranthinae), while Górniak et al. (2006) discuss relationships in Spiranthinae, Salazar et al. (2011a) examined relationships around Dichromanthus et al.; there adaptation to bird pollination has occurred in parallel, confusing generic limits, and Dueck et al. (2014) focussed on Spiranthes and its distribution.

For general phylogenetic relationships in Epidendroideae, see van den Berg (2005) and Górniak et al. (2010). Support for branching along the spine of Epidendroideae is not strong (e.g. Cameron et al. 1997; Pridgeon et al. 2001b; Cameron 2004). Palmorchis is sister to Neottieae, the combined clade being sister to all other Epidendroideae (Rothacker & Freudenstein 2006). Xiang et al. (2012; see also Freudenstein 2012) found at least three more clades, including Sobralia and Elleanthus, Nervilia and Tropidia respectively, to be successively sister to the rest at the base of the "higher Epidendroideae". These "basal" clades tend to lack articulated leaves, they have no velamen, and their pollinia are sectile/mealy (Pridgeon et al. 2005); if their position is confirmed, this will affect identification of apomorphies for the subfamily.

Within Dendrobieae, the speciose Dendrobium and many of its sections are turning out to be polyphyletic (Yukawa & Uehara 1996: vegetatively variable, florally perhaps less so; Yukawa et al. 1993, 1996, 2000; Clements 2003: ITS study, see also earlier work). The largely Old World and also very diverse Bulbophyllum is less studied, but the few (ca 60) New World species form a clade sister to the African taxa, the genus evolving in the general Southeast Asian region (Gravendeel et al. 2004; Smidt et al. 2011); Fischer et al. (2007) studied the Malagasy species. For a major study of Pleurothallidinae, see Pridgeon et al. (2001b); Pleurothallis is also not monophyletic (Chiron et al. 2012: focus on Brazilian species). Abele et al. (2005) and Matuszkiewicz and Tukallo (2006) discussed the phylogeny of Masdevallia, while Karremans et al. (2012) looked at relationships in Stelis, which has sometimes been extended to include "a few hundred" species of Pleurothallis. Russell et al. (2010) discuss phylogeny in the widely-distributed Polystachya (Vandeae: monopodial), where there is some correlation of polyploidy with broad species distributions. For relationships in and around Vanda, see Gardiner et al. (2013). Topik et al. (2005) investigated relationships in Aeridinae; characters conventionally used to establish relationships showed little congruence with the tree they obtained (see also Hidayat et al. 2005). For angraecoid orchids in general (Angraecineae), see Stewart et al. (2006), while Szlachetko et al. (2015: ITS) looked at relationships around Angraecum. For phylogenetic relationships in Laeliinae, see van den Berg et al. (2000), for diversification in Coelogyninae, see Gravendeel et al. (2005), for studies in Maxillarieae, see Whitten et al. (2000), Williams and Whitten (2003), Sitko et al. (2006), Arévalo and Cameron (2013), and especially Whitten et al. (2007: Maxillaria to be restricted, generic realignments needed) and in Oncidiinae, Williams et al. (2001a, b, 2005). For studies in Cymbidieae, see Whitten et al. (2005: Zygopetalinae), Neubig et al. (2008: Dichaea, Zygopetalinae), Cie&sacute;licka (2006) and Marios et al. (2014), both Eulophia, and Chase (1987), Chase and Palmer (1997), Williams et al. (2001), Chase et al. (2009) and especially Neubig et al. (2012a) all focusing on Oncidiinae and the polyphyletic Oncidium. For Epidendreae see Kulak et al. (2006), and in Pinheiro and Cozzolino( 2013) there is a summary of what is known about Epidendrum itself; nuclear and plastid DNA give conflicting signals in Cattleya (van den Berg 2015). For Sobralieae, see Neubig et al. (2011). Malaxis and Liparis, both with species in temperate as well as tropical regions, may not be monophyletic, but are closely intertwined (e.g. Cameron 2005a: Malaxideae); it is likely that they are secondarily terrestrial. For relationships in the Calanthe group, with plicate leaves and also largely terrestrial, see Zhai et al. (2014).

The recently described monotypic Pycnanthaceae from northwestern Argentina is indeed near Orchidaceae, as Ravenna (2011) suggested, but the description is inadequate (and the measurement units in the description are not always correct). The leaf sheaths are described as being closed, the flowers have a labellum, there are supposed to be three stamens with extrorse anthers, and the placentation is parietal. The type specimen looks like Malaxis (M. Chase, pers. comm.) and that is where it is to be placed (Nicola 2012).

Generic limits in the family are in the middle of a major overhaul to make them consistent with molecular findings, many of which have implications for clade/generic circumscriptions. In the past the importance of floral differences in separating genera was over-emphasized, but there has been widespread homoplasy in floral features (e.g. Chase et al. 2009 and references), for example, the distinctive lip-like appendage that was a defining feature of the old Corycinae (Waterman et al. 2009) seems to have evolved in parallel. Szlachetko et al. (2005 and references) give a statement of the "floral" position, maintaining that variation in column form, etc., yields taxonomically important characters (see also Szlachetko 1995; Rutkowski et al. 2008). However, clade limits suggested by molecular studies and generic limits suggested by floral features alone by no means always agree (Kocyan et al. 2008 and references). The features characterising the erstwhile broadly-delimited and polyphyletic Oncidium - mimicry of oil flowers of Malpighiaceae, whether or not the orchid also offers oil as a reward - is a good example of this (Williams et al. 2001; Neubig et al. 2008; Stpiczynaska & Davies 2008; Chase et al. 2009; esp. Neubig et al. 2012a), similarly, in Aeridinae there is also probably widespread parallelism in floral characters used to delimit genera (Hidayat et al. 2005; Salazar et al. 2011a, b for other examples). It is not that floral morphology is inherently taxonomically useless, but as elsewhere, undue reliance on it will lead us seriously astray if our interest is in understanding phylogeny. In some Epidendroideae vegetative variation may correlate better with clades evident in molecular phylogenies (e.g. Cameron 2005a), although anatomical variation by itself may suggest little major phylogenetic structure (Stern et al. 2004; Stern & Carlsward 2006). For generic limits in Maxillariinae, c.f. Whitten et al. (2007) and Szlachetko et al. (2012) and in Habenariinae, see Batista et al. (2013 and references).

There have been extensive discussions about generic limits in European Orchidinae (Tyteca & Klein 2008, 2009; Bateman 2009; Scopece et al. 2010b). In an attempt to make generic limits there more objective, Scopece et al. (2010b) found that clade membership correlated well with post-zygotic reproductive isolation (embryo death). A phylogeny-based classification in which this and other evidence was incorporated could, they thought, be defended on more explicit grounds, and this would allow morphologically distinctive taxa previously segregated as separate genera be incorporated into their proper clades (Scopece et al. 2010b). This approach is somewhat reminiscent of that of Danser (1929), and although perhaps useful in Orchidaceae - but it is going to be interesting to see how widely it can be applied even here, and what the taxonomic consequences are - it may be inapplicable to other angiosperms with different breeding behaviours.

Disagreements in generic circumscriptions may reflect fundamental differences in classificatory philosophies and differing beliefs in the ability of morphology when used alone alone to disclose relationships. However, even having a phylogeny and agreeing over basic taxonomic philosophies does not mean that there will be automatic agreement about generic limits. Thus Clements (2003, 2006) suggested a wholesale pulverization and reorganization of Dendrobium and its relatives. The species numbers given above do not reflect this, and Burke et al. (2008), Janes and Duretto (2010), Schuiteman and Adams (2011), and Schuiteman (2012) suggest that a broader circumscription of the genus would be preferable; species limits are also at issue here (Adams 2011: focus on Australia). Jones and Clements (2002a, esp. 2002b) divide Pterostylis; since the monophyly of Pterostylis s.l. was confirmed, the division is perhaps questionable (if one likes broadly-drawn generic limits), and indeed Janes and Duretto (2010) and Jones et al. (2010) suggest returning to the old circumscription of the genus. However, Clements et al. (2011) note that there were indeed nine or so identifiable groups around here. Jones et al. (2001) also dismember the monophyletic Caladenia and Clements et al. (2002) divide a monophyletic Corybas, as do Jones et al. (2002 - also much else). Such cases simply reflect conflicting preferences for narrow or broad genus limits, so they are something of a pain. In any event, in Australia, the result of nomenclatural changes made for these and other reasons is that about 45% of the species and subspecies in the entire orchid flora of some species have acquired new generic names in the brief period between 2000 and mid-2009 (Hopper 2009) - surely, this is Taxonomic Progress. Finally, Reveal (2012) came up with an earlier name for Epidendroideae (10 versus 58,500 hits - Google search iv.2012), but it will perhaps go the way of an earlier name that was found for Chloridoideae - oblivion. One can but hope for sense.

For an infrageneric classification of Vanilla, see Soto Arenas and Cribb (2010), and for an account of Anacamptis, Orchis, etc., see Kretzschmar et al. (2007). For a reclassification of Pleurothallidinae, see Pridgeon and Chase (2001); Pleurothallis was not monophyletic - but c.f. Karremans et al. (2012). This is a huge group, and sampling is still relatively very poor. There is some controversy about generic limits in the Masdevallia area, c.f. Luer (2006) and Pridgeon (2007), and reclassification of Maxillarieae is likely (Whitten et al. 2007); Blanco et al. (2007) made many new combinations. For generic limits around Angraecum, see Szlachetko et al. (2015), and those around Cattleya, see van den Berg (2014).

Chemistry, Morphology, etc. For the distribution of fructose oligosaccharides, see Pollard (1982) and Meier and Reid (1982). Although recorded there only for some Hypoxidaceae in the [Boryaceae [Blandfordiaceae [Lanariaceae [Asteliaceae + Hypoxidaceae]]]] clade, and not for some of the smaller families elsewhere in Asparagales, fructans seem to be widespread in this part of the tree; they were not recorded from Orchidaceae.

Age. This node can be dated around 67.1 or 42/65.2 m.y. (S. Chen et al. 2013: last two numbers should be the same?), m.y. (Janssen & Bremer 2004: but c.f. topology) or ca 93.3 m.y.a. (Magallón et al. 2015).

There are many dates for clades in this area in both Janssen and Bremer (2004) and Wikström et al. (2001), but the topologies there differ from that above; if relationships change, some ages may be of use.

Chemistry, Morphology, etc. For some information, see Kocyan and Birch (2011); there is extensive homoplasy in this little clade, so exactly where features like "septal nectaries external" are to be placed is unclear.

Phylogeny. Relationships between Milligania and Lanaria and Blandfordia were suggested by Bayer et al. (1998a). Kocyan and Birch (2011: all genera studied) found that Lanariaceae, Asteliaceae and Hypoxidaceae formed a trichotomy, while Seberg et al. (2012) found that jackknife support for the clade was poor, and that Asteliaceae and Lanariaceae reversed their positions, i.e. to [Asteliaceae [Lanariaceae + Hypoxidaceae]], and relationships were also scrambled in Janssen and Bremer (2004) and Wikström et al. (2001).

Ecology & Physiology.Borya has tuberculate roots that may have the coil-forming Rhizoctonia fungus is them (c.f. Orchidaceae); the plant is arborescent and dessication-tolerant (e.g. Barthlott 2006) and has vessels with almost simple perforation plates in the stem (Carlquist 2012a).

Chemistry, Morphology, etc. The pedicels of Alania have
several bracteoles.

Additional information is taken from Dahlgren et al. (1985) and Conran (1998), both general, and Conran and
Temby (2000: floral morphology).

Previous Relationships. Genera of Boryaceae have often been included in Anthericaceae (= Asparagaceae-Agavoideae), as by Takhtajan (1997).

Age. The age of this clade is estimated at (98-)81, 74(-56) m.y. by Bell et al. (2010: note topology), at ca 57.7 or 38.3 m.y. by S. Chen et al. (2013), and about 84.5 m.y.a. by Magallón et al. (2015).

Chemistry, Morphology, etc. Information is taken from Clifford and
Conran (1998: general), Di Fulvio and Cave (1965) and Prakash and Ramsey (2000: both embryology) and Kocyan and Endress (2001b: some floral morphology.

Previous Relationships. Rudall (2003a) suggested that there was a close morphological relationship between Boryaceae and Blandfordiaceae.

Evolution.Divergence & Distribution. For the biogeography of the family see Birch et al. (2008, 2011, esp. 2012); there has been extensive long-distance dispersal, and Asteliaceae seem to have been around in New Zealand in the Oligocene, when the island was all or mostly under water... One species of Astelia is known from Réunion (see map). For the Mascarenes/Africa-Hawaii/Antipodes connection, see also Malvaceae (Kokia), Asteraceae (Hesperomannia); Keeley and Funk (2011) give a list of Hawaiian endemics, also see Acacia (Fabaceae).

Given current ideas of relationships in the family (see below), character evolution in it will repay investigation.

Chemistry, Morphology, etc. Carlquist (2012a) suggested that vessels were practically absent, except perhaps in the roots - although this might depend on the technique used to prepare the material.

For additional information, see
Prakash and Ramsey (2000: embryology), and Brittan et al. (1987) and Bayer et al. (1998a), both general,
for information.

Phylogeny. The phylogeny of the family has been clarified by Birch et al. (2009); Milligania, with loculical capsular fruits, a semi-inferior ovary and no intra-ovarian trichomes, perfect flowers, etc., and often considered rather different from other Asteliaceae, seems to be embedded in Astelia, as do the other small genera previously recognized in the family (Birch et al. 2008, esp. 2009). However, Birch et al. (2012) found that [Neoastelia + Milligania] were sister to the rest of the family; Astelia is to include Collospermum.

Age. Crown group Hypoxidaceae have been dated to as much as ca 78 m.y.a. (Janssen & Bremer 2004) and as little as ca 22.9 or 15.6 m.y. by S. Chen et al. (2013).

Hypoxidaceae can be recognised by their rosettes of
plicate or at least folded leaves and persistent leaf bases; non-glandular
indumentum is quite prominent. In the
flowers, the outer whorl of tepals tends to be green outside and the ovary is
inferior and sometimes subterranean; it is often narrowed and beaked at the apex.

Evolution.Pollination Biology & Seed Dispersal. Pollen is the main reward, and flies of various kinds, beetles and bees seem to be the pollinators (Kocyan et al. 2011 for a summary). At least some species of Hypoxis are apomictic (Nordal 1998).

Chemistry, Morphology, etc. Kocyan (2007) found that some flowers of Curculigo racemosa were polyandrous, however, the stamens were not fasciculate. The staminodes of Pauridia that are adnate to the style rather surprisingly appear to represent the outer androecial whorl - and they are responsible for reports of a 6-lobed stigma in the family. The rostrum, a narrowed, beak-like apical part of the ovary, appears to have evolved more than once, but its function is uncertain; the beak may also be formed by the connate tepals.

There is controversy over the tapetum type in the family and in the numbers of nuclei in the cells, and whether or not there is a velamen in the root. The ovules have a parietal cell, so are not tenuinucellate [?incorrect - not in the literature I have read]. The endosperm is reported as being nuclear or helobial; if the former, then the antipodal cells tend to persist (de Vos 1948, 1949).

Previous Relationships. Rudall (2003a) suggested that there might be a close morphological relationship between Hypoxidaceae and Orchidaceae. In older classifications, Hypoxidaceae were included in Amaryllidaceae.

Age. For the age of this node, some (93-)79, 70(-59) m.y., see Bell et al. (2010), ca 64.1 or 34.1 m.y., see S. Chen et al. (2013), and ca 79.7 m.y.a., see Magallón et al. (2015). The divergence of Ixoliriaceae is dated to ca 112 m.y. and that of Tecophilaeaceae to 108 m.y. (Janssen & Bremer 2004: note topology).

Chemistry, Morphology, etc. The outer tepals in at least some Iridaceae (and Orchidaceae!) are also mucronate to aristate.

Phylogeny. There is weak to moderate support for this taxon pair in Chase et al.
(2000a), Pires et al. (2006), Givnish et al. (2006) and Seberg et al. (2012), and stronger support in Graham et al. (2006: sampling poor); they have a very long branch in
the three-gene analysis of Fay et al. (2000). Davis et al. (2004) found some support for the clade [Ixoliriaceae + Iridaceae], although sampling was poor; Chase et al. (2006) found strong support for this relationship. Janssen and Bremer (2004) found pectinate relationships here: [Ixoliriaceae [Tecophilaeaceae [Doryanthaceae + the rest]]], while the relationships [Tecophilaeaceae [Doryanthaceae [Ixoliriaceae + Iridaceae]] the rest] in Chase et al. (2006) had very little support.

Previous Relationships. Both Dahlgren et al. (1985) and Takhtajan (1997) recognised relationships between Ixoliriaceae and Tecophilaeaceae, as well as with a selection of other asparagalean families.

Tecophilaeaceae are cormose herbs sometimes with broad-bladed, petiolate leaves; their flowers have spreading tepals and are often monosymmetric because of the androecium, the stamens being strongly dimorphic. The anthers open by pores.

Evolution.Divergence & Distribution. Buerki et al. (2013a) discussed the complex eco-biogeographical history of this small clade, i.a. they noted that its colonization of what are now Mediterranean ecosystems occurred before the origin of the Mediterranean climate, as seems to be common (see also Vargas et al. 2014).

Chemistry, Morphology, etc. This is a heterogeneous group. Cells adjacent to
stomata in Cyanastrum were described as having parallel cell divisions
by Tomlinson (1974). The monosymmetry of the flower is
largely caused by the androecium; enantiostyly also occurs in a few species of Cyanella. Odontostomum has been reported to have six staminodia alternating with the six stamens; the "staminodia" are some kind of corona or other enation from the tepals.

Some information is taken from Rudall
(1997), Simpson and Rudall (1998), Brummitt et al. (1998) and Manning and Goldblatt (2012), that on ovules, from Nietsch (1941), and that on seedlings, which are variable in their morphology,
from Tillich (1996a, 2003).

Phylogeny.Tecophilaea was found to be sister to the rest of the family, although with only moderate support; other relationships along the backbone were poorly resolved (Brummitt et al. 1998). More recently, Buerki et al. (2013a) found that the clade [Conanthera + Zephyra] (both genera are from South America) were sister to the rest of the family.

Classification. Given the poor support for many relationships here, a classification is premature (c.f. Brummitt et al. 1998); despite a more resolved phylogeny, Buerki et al. (2013) quite reasonably elect not to develop any formal suprageneric hierarchy.

Age. this node has been dated to ca 107 m.y.a. (Janssen & Bremer 2004); the separation of Doryanthaceae from Iridaceae (sic) has been estimated at ca 82 m.y. (Goldblatt et al. 2008).

Pollen fossils assigned to Iridaceae-Isophysis or to Doryanthes have been found in Late Cretaceous rocks ca 75-70 m.y. old from Eastern Siberia (Hoffmann & Zetter 2010).

Phylogeny. There is only moderate support for this position in Fay et al. (2000) and practically no support in Seberg et al. (2012), but 92% bootstrap support in Graham et al. (2006: note sampling); see also Janssen and Bremer (2004).

Doryanthaceae are massive, tufted, perennial monocots; the leaves have entire margins although they disintegrate into fibres at the apex. Their dense inflorescences are borne at the end of long (up to 6 meters), unbranched, leafy stems and bear numerous large, radially symmetric, bright red flowers with inferior ovaries. The filament disappears into what looks like a tubular anther.

Chemistry, Morphology, etc. Kocyan and Endress (2001b) note that the connective is massive, each stamen being supplied by 2-4 "vascular complexes", although these were not observed by Newman (1928, 1929). There may be a hypostase immediately beneath the embryo sac, although there is also a great amount of tissue between it and the chalazal bundle (Newman 1928).

Much general information is taken from Wunderlich (1950) and
Clifford (1998); Blunden et al. (1973) described leaf anatomy, and Tillich (2003) described seedling morphology.

Evolution.Divergence & Distribution. A distinctive pattern of secondary growth is scattered through this clade, and has also been reported from Eriocaulaceae (Poales: Scatena et al. 2005). A meristem cuts off tissue to the inside, and there separate vascular bundles embedded in ground tissue differentiate (Rudall 1991, 1995b for records and literature). Mangin (1882) had suggested there might be a connection between the origin of this secondary thickening and the reticulum of vascular bundles in association with which "adventitious" roots arise in monocots.

Genes & Genomes. The loss of Arabidopsis-type telomeres is not simple; human-type telomeres ((TTAGGG)n)) may predominate, but there are other types, too. Asparagaceae-Scilloideae agree with other members of this clade, although the Arabidopsis-type telomere is somewhat more common than in the other members sampled (Adams et al. 2001; especially Sýkorová et al. 2003b, 2006a, b). Acanthocarpus, alone among the taxa discussed there as being an out-group, also lacks the telomere, but it is in fact a member of Asparagaceae-Lomandroideae (ex Laxmanniaceae), an ingroup, not Dasypogonaceae, a commelinid.

Chemistry, Morphology, etc. Glucomannan seed reserves are reported from at least some members of this clade - Iridaceae, Asparagaceae-Asparagoideae and -Scilloideae-Ornithogaleae - and they are also known from some Liliales; the vegetative plants also may have distinctive carbohydrates (Jakimow-Barras 1973; Meier & Reid 1982; Buckeridge et al. 2000). Apparently there are only tracheids in the xylem (Fahn 1990). For secondary growth - the continued activity of the primary thickening meristem - see also Cheadle (1937), Rudall (1995b) and Carlquist (2012a). Al;though there is sometimes a transition from collateral to amphivasal vascular bundles as the secondary thickening phase takes over, this is by no means always so (e.g. Diggle & DeMason 1983; Rudall 1984).

Phylogeny. A group with quite strong support
in Fay et al. (2000) and Soltis et al. (2007a), etc., but lacking much jackknife support in Seberg et al. (2012: bootstrap support better).

Iridaceae may be recognised by their often two-ranked, isobifacial leaves and their usually large flowers with showy tepals, three extrorse
anthers, a conspicuous and complex stigma, and an inferior ovary.

Evolution.Divergence & Distribution. It is suggested that Iridaceae were originally Antarctica-Australia, the family achieving its current distribution by a mixture of long-dstance dispersal across a proto-Indian Ocean and migration via west Antarctica to Africa and the New World where the family is currently most diverse (e.g. Sanmartín & Ronquist 2004; Golblatt et al. 2008).

Davies et al. (2005) noted that in Iridaceae diversification was greater in areas like southern Africa than in the northern hemisphere, and there were clades with a disproportionately large number of species in e.g. southern Africa. The Cape area is notably diverse from a global point of view (Kreft & Jetz 2007), and Iridaceae are one of the major geophytic groups of the Cape (Procheŝ et al. 2006) with more than 650 species there. Davies et al. (2004c) see this diversification as the result of the interaction of local features such as traits affecting reproductive isolation and the ecological and climatic heterogeneity of the area. Valente at al. (2012) suggested that pollinator shifts had helped drive speciation in southern African Gladiolus, although other factors were also involved. For the radiation of the Cape genus Moraea, both cytologically and florally diverse, see Goldblatt et al. (2002); radiation in this and other iridaceous Cape genera may have begun in the fynbos in the Miocene some 25 m.y.a., divergence in the succulent Karoo being more recent (Verboom et al. 2009). Diversification of two geophytic Cape genera, Babiana, with ca 92 species nearly all from the Greater Cape floristic region, and Moraea, with over 150 species in Cape region, may in part be connected with soil type preferences changing during speciation; here diversification began a mere 17-15 m.y.a. in the mid-Pliocene (Schnitzler et al. 2011); diversification rates in the Cape region and outside are largely similar (Silvestro et al. 2011).

Pollination Biology & Seed Dispersal. Iridaceae show considerable floral diversification, ranging from the open flowers of Sisyrinchium to the meranthia of Iris et al. and the tubular flowers of Gladiolus et al. (e.g. Bernhardt & Goldblatt 2006; Goldblatt & Manning 2006 and references; Rodrigues & Sytsma 2006; Wilson 2006). In Iris and its relativesthe flower will appear to the pollinator as if were really three monosymmetric flowers. There the tepaloid style overarches the stamen opposite it and the landing platform for the pollinator is a member of the outer perianth whorl underneath the style/stamen complex. However, in Cypella the three landing platforms for the pollinating bee are members of the inner perianth whorl. Here the pollen deposited on the backs of the bees comes from half anthers of adjacent stamens and is deposited on the receptive surfaces of two adjacent half-stigmas (Vogel 1974).

The flowers of Gladiolus (Crocoideae) are obliquely monosymmetric, although this is hardly apparent in the open flower due to changes in orientation as the flower and inflorescence grow. Tepal patterning, where it occurs, is usually on an adaxial lateral member of the outer whorl and adjacent members of the inner tepal whorl and is clearly on the adaxial side of the flower, but it may be on an adaxial lateral and the abaxial member of the outer whorl and a tepal of the inner whorl between them (Eichler 1875; Choob 2001). Although it is likely that other Crocoideae show the same oblique monosymmetry, monosymmetry in genera like Diplarrena (Iridoideae) and Sparaxis is vertical and with normal monocot orientation; Diplarrena has only two stamens and one staminode. Interesting infraspecific variation occurs. In some flowers of Crocosmia X crocosmiiflora the odd member of the outer whorl was adaxial while in others it was abaxial; the patterning of the tepals, etc., varied accordingly (pers. obs.). All told, well over half the family has monosymmetric flowers of one sort or another, and the evolution of monosymmetry in the family will repay further study (see also Davies et al. 2004b).

Much work has been carried out on pollination in Iridaceae bu Peter Goldblatt and John Manning. Species from the sub-Saharan region, especially in South Africa, have been the focus of their research. Nearly all species are morphologically specialized and are pollinated by non-specialist (if sometimes highly specialized) pollinators (Goldblatt & Manning 2006, 2008 for general accounts; Johnson 2010). Floral homoplasy is very extensive in Iridoideae-Tigridieae (Rodrigues & Sytsma 2006), -Trimezieae (Lovo et al. 2012), and -Irideae (in Iris itself - Wilson 2006). Many different kinds of pollinator are involved. Thus Babiana (Crocoideae) is pollinated by birds, scarab beetles, bees, moths, etc. (Bernhardt & Goldblatt 2006; esp. Goldblatt & Manning 2007), while scarabeid monkey beetles pollinate the flowers of three Cape genera of Iridaceae that have distinctive dark markings at the bases of the tepals (van Kleunen et al. 2007). Valente at al. (2012) examined pollination in southern African Gladiolus, recording numerous gains and losses of 5/7 of the pollination syndromes (the other two were decidedly uncommon), with long-tounged bee pollination being acquired at least four or twelve times (depending on the method used), but lost twice as frequently or more.

At least 34 species of southwest African Iridaceae are known to be pollinated by three species of (extremely) long-tongued dipteran nemestrinid flies, and all told slightly over 10% (117 species) of the 1,025 species of Iridaceae in southern Africa have such pollinators. The long-tubed monosymmetric flowers pollinated by these flies have evolved several times here as well as in unrelated groups (Manning & Goldblatt 1996, 1997; Goldblatt & Manning 2000, 2006), and Karolyi et al. (2013) discuss how the flies take in the nectar. This compares with a mere 64 species of Iridaceae in the same region that are bird pollinated and over 550 species that are pollinated by long-tongued Apidae (Goldblatt & Manning 2006). There are a number of oil flowers in Iridaceae, including Cypella (see above), ca 35 species of Sisyrinchium from South America, and some other New World Iridoideae like Tigridia (Renner & Schaefer 2010); oil-secreting trichomes appear to have evolved twice in Sisyrinchium alone (Chauveau et al. 2011). Indeed, these trichomes vary both in morphology and position in flowers of New World Iridaceae (Silvério et al. 2012); evolution of floral rewards in these taxa has a complex pattern of gains, changes and losses (Chauveau et al. 2012).

Vegetative Variation. Some Iridaceae are more or less woody, and monocot-type secondary thickening has been reported from them; the vessel elements in the roots of such plants often have scalariform perforation plates (Cheadle 1964: inc. Klattia). Foliar variation is considerable. Leaves may be terete and unifacial, apparently ordinary and heterobifacial (even some Iris), or - commonly - ensiform and isobifacial, as in Gladiolus and most Iris, while others are strangely ribbed, but in transverse section they all seem to be modifications of a basic unifacial leaf theme (e.g. Ross 1892, 1893; Arber 1925; Rudall 1991); Geissorhiza alone has ligulate leaves. Crocus has revolute leaves with a unifacial midrib, and Romulea seems to be a modification of
this. For water-catching leaves of Iridaceae with very distinctive morphologies that are found especially in taxa from Namaqualand, South Africa, see Vogel and Müller-Doblies (2011).

Genes & Genomes. Moraes et al. (2015) looked at chromosome number evolution in Iridoideae (the numbers are very variable), and also gave some 2C values. Although polyploid species had the highest 2C values, both polyploids and diploids had medium-sized to small genomes. For cytological evolution in Crocus, n = 3

Chemistry, Morphology, etc. For the occurrence of plumbagin in Aristea, see Harborne and Williams (2001). Homeria and Moraea (Iridoideae) have bufadienolides (cardiac glycosides: Harborne & Williams 2001). Iris contains a greater diversity of isoflavonoids than any other group outside Fabaceae (Reynaud et al. 2005); for xanthones, especially in Iris, see Williams et al. (1997b).

Goldblatt
(1990) interpreted the paired "bracts" below the single flowers of Isophysis
as representing a reduced rhipidium, a monochasial cymose inflorescence - a rhipidium may then be another synapomorphy for
the family. Some species of Nivenia are heterostylous, a very uncommon condition in the monocots. Aristea is palynologically very variable, some members even having disulcate pollen (see Goldblatt & Le Thomas 1997; le Thomas et al. 2001). In Sisyrinchium and its relatives the style branches alternate with the stamens; elsewhere the two are usually on the same radius. For a discussion of the caruncles/arils of Iris, see Wilson (2006).

Phylogeny. Iridaceae are monophyletic in nearly all studies (but c.f. Chase et al. 1995a). Initial resuls suggested that the monotypic Isophysidoideae were sister to the rest of the family, Crocoideae and Iridoideae appeared to be monophyletic, but the status of Aristeoideae was unclear. Reeves et al. (2001a, b: four genes) found that Patersonia, Geosiris, and Aristea were successively sister to a large clade making up [Aristeoideae + Crocoideae]; support was mostly moderate (see also Teixeira de Souza-Chies et al. 1997). If these relationships were confirmed, either the circumscription of Crocoideae would have to be considerably extended, or three more subfamilies would be needed. Goldblatt et al. (2008: five plastid genes) took for this latter option; they found strong support for the pectinations basal to Crocoideae s. str., albeit using successive weighting, which tends to leave one a little uneasy. See Rudall (1994c) for a morphological phylogeny.

Within Iridoideae, the Australian Diplarrhena, whose monosymmetric flowers have only two stamens and pollen grains that are spherical, inaperturate, and intectate pollen, may be sister to the rest (Reeves et al. 2001a, b; Rudall et al. 2003a). The five tribes in Iridioideae are quite well supported and have well-resolved relationships: [Diplarreneae [Irideae [Sisyrincheae [Trimezieae + Tigridieae]]]] (Goldblatt & Manning 2008; also Golblatt et al. 2004, 2006). For diversification of the American Tigridieae, see Rodrigues and Sytsma (2006). Relationships within Trimezieae are being clarified (Lovo et al. 2012). For a phylogeny of Iris, see Tillie et al. (2001) and Wilson (2004); there is phylogenetic resolution of the major groups in the genus (Wilson 2011), although some of the characters used to distinguish groups in the past, such as sepal crests (ridges or more elaborate structures down the midrib of the outer perianth whorl) have turned out to be homoplasious (Guo & Wilson 2014). Karst and Wilson (2012) obtained a fair degree of resolution in relationships within New World Sisyrinchium, although species limits there are in a considerable state of disarray (see also Chauveau et al. 2011).

Within Crocoideae there are five tribes, but these were mostly only moderately supported and their relationships poorly resolved (Goldblatt & Manning 2008; also Goldblatt et al. 2004). Tritoniopsis, with a tubular cotyledonary sheath and tubular cataphyll, may be sister to the rest of the subfamily, but support is at best moderate (Goldblatt et al. 2006; Golblatt & Manning 2008). For a phylogeny of Crocus see Petersen et al. (2008, c.f. in part Frello et al. 2004), and especially Harpke et al. (2013). See Goldblatt and Manning (1998) for a treatment of much of Gladiolus. For relationships within Gladiolus, see Valente et al. (2011, 2012); although there was some resolution towards the base of the tree, many species, especially those from southern Africa, could not be distinguished in these studies.

Classification. I follow the classification suggested by Goldblatt et al. (2008); the subfamilies are for the most part well characterised. See Wilson (2011) for an infrageneric classification of Iris.

Phylogeny. This is a strongly supported group in Fay et al. (2000) and Soltis et al. (2007a); see also Janssen and Bremer (2004). The loss of the mitochondrial rpl2 gene occurs either at this node or the next up the tree (see Adams et al. 2002b).

Xeronemataceae are large monocot herbs that may be recognised by their
two-ranked isobifacial leaves and congested, brush-like inflorescences with bright red, rather large, radially symmetric, and upwardly-facing
flowers. The stamens are strongly
exserted.

Chemistry, Morphology, etc. The family is little known, although there is some information in
Chase et al. (2000c); the style is scored as if it is hollow in Rudall (2003a).

Previous Relationships. Xeronemataceae were provisionally
placed in Asphodelaceae by Takhtajan (1997) and in Hemerocallidaceae by
Clifford et al. (1998).

Evolution.Divergence & Distribution. For the optimisation of characters like "septal nectaries infralocular" and "ovary superior", see the beginning of this page. The optimisation of successive microsporogenesis on the tree is also uncertain (Chase et al. 2000a); for instance,
microsporogenesis varies within Xanthorrhoeaceae.

Chemistry, Morphology. Gatin (1920: broad sampling across Liliaceae s.l.) found that taxa that have tepals with single vascular traces are common in this clade, although some have three or more traces; she also studied many other details of pedicel vasculature. Schnarf and Wunderlich (1939) provide some embryological details and El-Hamidi (1952) some for the gynoecium from scattered taxa in "Asphodeloideae"; the latter found substantial similarity between all the taxa he examined except Aphyllanthes. For chromosome sizes of a number of taxa in the group, see Vijayavalli and Mathew (1990 - as Liliaceae).

Phylogeny. This clade has strong support in Fay
et al. (2000) and Chase et al. (2000b).

Age. This crown group is dated to ca 90 m.y. (Janssen & Bremer 2004). Bell et al. (2010), on the other hand, estimate an age of (66-)52, 47(-36) m.y., S. Chen et al. (2013) of 55.6 or 47.1 m.y.a., while (85-)74, 68(-60) m.y. is the age in Crisp et al. (2014) and 52.3 m.y.a. in Magallón et al. (2015).

Age. The age of this node is ca 52.5 or or 46.4 m.y. (S. Chen et al. 2013). Note the age of Xanthorrhoea stem in Crisp et al. (2014) is based on the toplogy [Hemerocallidoideae [Xanthorrhoeoideae + Asphodeloideae]].

Age. Crown-group Xanthorrhoeoideae are estimated to be a mere 1.7 or 1 m.y.o. (S. Chen et al. 2013) or (59-)35-24(-13) m.y. (Crisp et al. 2014), although the latter also obtained some very young ages, most (13-)6.4, 3.3(-1.8) m.y.a., one somewhat older. Crisp et al. (2014) preferred the older (first) set of estimates, which came from using a random local clocks model, over the younger ages, which came from an uncorrelated lognormal relaxed clock model; the latter, they thought, could not handle the substitution rate changes.

Xanthorrhoeoideae can be recognised by their habit. They have a dense tuft of long, narrow leaves terminating a stout, woody stem (and persisting as a skirt of dried leaves if there are no fires) and an long, erect, densely spike-like inflorescence with small flowers and capsular fruits.

Evolution.Divergence & Distribution.Eccremis
and Pasithea represent independent migrations of the phormioid clade to South America (Wurdack & Door 2009), while Bulbinella (Asphodeloideae) grows in South Africa and New Zealand.

For an ecological account of Xanthorrhoea, see Lamont et al. (2004); some diversification in the genus may be associated with the aridification of the Nullarbor Plain some 14-13 m.y.a. that separated eastern and western clades (Crisp & Cook 2007).

Pollination Biology & Seed Dispersal. Many species of the large genus Aloe (Asphodeloideae), perhaps some 85 species in southern Africa alone, are pollinated by birds (Rebelo 1987), but insect pollination is also knownt here, perhaps especially among the short-tubed species (Symes et al. 2009; Hargreaves et al. 2008, 2012), as in other groups of Asphodelaceae. Buzz pollination probably predominates in Hemerocallidoideae, and the small pollen (but c.f. Arnocrinum and Hemerocallis itself), although not the presence of pollenkitt, is consistent with this (Furness et al. 2014)

A number of Hemerocallidoideae have myrmecochorous seeds (Lengyel et al. 2010).

Vegetative Variation. Most members of the phormioid clade have leaves that are more or less isobifacial immediately above the sheath, but higher up they become dorsiventrally flattened and more "normal" in appearance; Pasithea, sister to the rest of the clade, lacks this isobifacial zone (Wurdack & Dorr 2009). Members of Asphodeloideae have more or less succulent leaves, and species of Aloe and Haworthia in particular are commonly rosette plants with massively fleshy leaves; these can be borne in spirals or be distinctively two-ranked. As with Aizoaceae from southern Africa, there is great variation in the micromorphology of their epidermis (Cutler 1982); the two grow in similar extreme habitats. For the remarkable water-catching leaves in taxa growing in foggy deserts in Namaqualand, South Africa, see Vogel and Müller-Doblies (2011). Geitonoplesium (Hemerocallidoideae) has resupinate leaves.

Chemistry, Morphology, etc. Within Asphodelaceae, the old Alooideae (= Asphodeloideae, part) are chemically very distinctive (Klopper et al. 2010 for a summary). Aloin, an anthraquinone glycoside, is a laxative commonly found in Aloe. Members of the old Alooideae have 1-methyl-8-hydroxyanthraquinones, e.g. chrysophanol, in the roots and anthrone-C-glycosides in the leaves (e.g. Manning et al. 2014). In Asphodeloideae Bulbine, Trachyandra, and Kniphofia all have knipholone, an anthraquinone derivative (van Wyck et al. 2005), but it appears not to have been reported from the Asphodelus clade. Johnsonia (Hemerocallidoideae)
has chelidonic acid (Ramstad 1953).

The apical meristem of the stem in Xanthorrhoea media is massive - 580-1283 µm across (Staff 1968, q.v. for details of stem growth). The sieve tube
plastids of the Aloe group also have peripheral fibres in addition to the central protein crystal. Aloin cells are reported from Dianella (Hemerocallidoideae: see Rudall 2003a); on the other hand, Kniphofia lacks aloin cells, having a well developed sclerenchymatous cap in their place (as have some other Asphodelaceae, even some Alooideae). It is unclear if aloin cells are secretory (Beaumont et al. 1985: survey and chemistry). The vascular bundles in the leaf form a
circle and there are globules in the outer bundle sheath (also in Kniphofia); the central cells of the leaf are gelatinous. The old Aloideae are reported to have tetracytic stomata (e.g. Cutler 1972), although this is questioned by G. Smith and van Wyk (1992).

The inflorescences of Xanthorrhoea are described as being terminal (Clifford 1998); I do not know if they are always terminal in Asphodeloideae. Hemerocallis also seems to have lateral bracteoles, as does Dianella; both may have "inverted" flowers (e.g. Eichler 1875; Ehrhardt 1992), although in Hemerocallis, at least, this seems to be variable. Hemerocallis flowers with the median outer tepal adaxial are common, but the seal of the Daylily Society shows a flower with the normal monocot orientation! The number of vascular bundles supplying the tepals in members of this subfamily varies from (1-)3-9(-25) (Clifford et al. 1998a). The floral monosymmetry in Haworthia and relatives is rather weak. Hemerocallidoideae often have rather elaborate stamens. Both Hemerocallidoideae and Xanthorrhoeoideae have ovaries that can be interpreted as being secondarily superior and that have infra-locular septal nectaries (Rudall 2002, 2003a). In at least some species of Aloe the larger stamens are opposite the inner whorl of tepals. Ovule orientation at the basal node in the family is unclear (c.f. Steyn & Smith 1998). Kniphofia has
a bistomal micropyle and a nucellar endothelium (Takhtajan 1985). Daru et al. (2013) noted that seedlings of Aloe and Gasteria have two-ranked leaves, whatever the leaf arrangement in the adults.

Microsporogenesis in Hemerocallis was described as being
successive and the endosperm as being nuclear
by Di Fulvio and Cave (1965, but c.f. Cave 1955). Hemerocallis also has isoflavones,
monosulcate pollen and a wet stigma, but it lacks a nucellar cap and septal
nectaries. In pollen morphology Hemerocallis was considered to be derived by
Chase et al. (1996); with Simethis), which has trichotomosulcate pollen, it is sister to the rest of Hemerocallidoideae (see also McPherson et al. 2004; Wurdack & Dorr 2009; Furness et al. 2014 - is microsporogenesis in the latter known?); monosulcate pollen then represents a reversal here.

For Xanthorrhoea, some information is taken from Chanda and Ghosh (1976: pollen), Rudall (1994b: embryology), Rudall and Chase
(1996: phylogeny) and Bedford et al. (1986) and Clifford (1998), both general.

Phylogeny. There is strong support for Xanthorrhoeaceae s.l. in Fay et al. (2000), Wurdack and Dorr (2009), etc. However, relationships within the clade were initially unclear. There is slight support for a [Xanthorrhoeoideae + Asphodeloideae] clade in the three-gene tree of Chase et al. (2000a; see also Fay et al. 2000; Crisp et al. 2014: chloroplast genes); some analyses in Chase et al. (2000a) also suggested an [Asphodeloideae + Hemerocallidoideae] clade. Hemerocallidoideae, and perhaps also Asphodeloideae, were paraphyletic in a rpb2 analysis of Crisp et al. (2014: ?rooting). However, Devey et al. (2006) found support for a [Xanthorrhoeoideae + Hemerocallidoideae] clade (see also Pires et al. 2006; Graham et al. 2006; Wurdack & Dorr 2009: good-moderate support; Seberg et al. 2012; Steele et al. 2012: strong support). Rudall (2003a) suggested that there were close morphological relationships between Hemerocallidaceae (Hemerocallidoideae) and Asphodelaceae (Asphodeloideae) - and between Xanthorrhoeaceae s. str. and Iridaceae...

Within Asphodeloideae, Aloe and its immediate relatives (= Alooideae s. str.: Klopper et al. 2010 for a summary) seem distinct and form a monophyletic group. However, more ordinary-looking Bulbine
is sister to this clade, and then come other Asphodeloideae, including Kniphofia et al. and Eremurus et al., which together form a clade (Naderi Safar et al. 2014); the [Asphodelus + Asphodeline] clade is sister to the rest of the subfamily, and with good support (n = 14) (see Devey et al. 2006 for a phylogeny, inc. details of that of Bulbine, also references below). Ramdhani et al. (2009) discussed the phylogeny of Kniphofia. Some species of Bulbine have a bimodal karyotype of n = 7, 4 long and 3 short (Spies & Hardy 1983), rather like the karyotype of Aloeae (4L + 3S: probably evolved independently, see Chase et al. 2000a; Devey et al. 2006; Pires et al. 2006), and they also have similar medicinal properties... For relationships around Aloe, which remained poorly understood and little resolved for some time, see Treutlein et al. (2003a, b), and for those around Haworthia, see Ramdhani et al. (2011). Daru et al. (2013) and in particular Manning et al. (2014) have clarified relationships there, although support for some of the basal branches could be improved, and both Aloe and Haworthia are scattered through the tree.

Classification. A.P.G. II (2003) suggested as an option the inclusion of Asphodelaceae, Xanthorrhoeaceae and Hemerocallidaceae in Xanthorrhoeaceae s.l., and this circumscription was adopted by A.P.G. III (2009). The subfamilial classification above follows that in Chase et al. (2009b). The recognition of an Alooideae (= Asphodeloideae: Aloeae) would make Asphodeloideae paraphyletic and necessitate the recognition of several other subfamilies.

G. Smith and Steyn (2004) discuss the taxonomy of Alooideae; generic limits around Aloe are
decidedly unsatisfactory. However, Grace et al. (2013) and in particular Manning et al. (2014) have revised the classification of the whole group, recognising 11 genera.

Species limits are problematic in Aloe, in Kniphofia (Ramdhani et al. 2009), and in Haworthia (Ramdhani et al. 2011: ?hybridization; Bayer 2009: some comments and references), both Alooideae. Species estimates in Dianella (Hemerocallidoideae) range from 25-350+ (Carr 2007).

Thanks. I thank Syd Ramdhani and Matt Ogburn for useful discussions.

Previous Relationships. Three genera that used to be placed in Asphodelaceae s. str. are now in Hemerocallidoideae (Simethis),
Asparagaceae-Asparagoideae (Hemiphylacus), and Asparagaceae-Agavoideae (Paradisea, Anthericaceae s. str.) respectively - the evidence is largely molecular (Chase et
al. 2000b).

Chemistry, Morphology, etc. Where do steroidal saponins occur in this clade? Microsporogenesis is uniform here. In other Asparagales with successive microsporogenesis, details of wall formation (centrifugal cell plates) is similar to those members of this clade that have been studied, however, plate formation may also be centripetal when microsporogensis is simultaneous (Nadot et al. 2006). For chromosome size in Liliaceae s.l. and relatives, i.e. some taxa in this area, see Vijayavalli and Mathew (1990).

Phylogeny. This is a strongly supported clade (e.g.
Chase et al. 1995a; Fay et al. 2000; Chase et al. 2000b; Graham et al. 2005), however, inclusion of Aphyllanthes in analyses has tended to decrease support for the clades within it (Graham et al. 2006). Kim et al. (2011: seven genes, three compartments) found that Amaryllidaceae grouped with Asparagoideae, Lomandroideae and Nolinoideae; other members of this clade formed a separate group.

Bacterial/Fungal Associates. Fungi on Allium and other Allioideae are rather different from those on Amaryllidoideae (e.g. Savile 1962).

Chemistry, Morphology, etc. Distinctive, mannose-binding lectins (the specificity is absolute) are found in Allioideae and Amaryllidoideae (van Damme et al. 1991: known from Agapanthus?). Very large genomes with a C value of some 350 picograms or more are found in some Amaryllidaceae-Allioideae and -Amaryllidoideae - also in Asparagaceae-Scilloideae (Leitch et al. 2005). For tapetal cells, see Wunderlich (1954), for inflorescence structure, see Weberling (1989).

Classification. Combining the three families Agapanthaceae, Alliaceae and Amaryllidaceae into Alliaceae s.l. was an option in A.P.G. II (2003), an option that was exercised in A.P.G. III (2009), although under the name of Amaryllidaceae. The infrafamial classification follows that in Chase et al. (2009b).

Agapanthoideae are robust, rhizomatous herbs that can be
recognised by their rather fleshy and two-ranked leaves and their scapose
umbellate inflorescence of generally large flowers with superior ovaries.

Allioideae can be recognised by their smell, their often
rather fleshy and soft leaves, and their scapose umbellate inflorescence with
medium-sized flowers that have superior ovaries.

Evolution.Divergence & Distribution. Nguyen et al. (2008) found that Old and New Word species of Allium are mostly in two separate clades, although basal to the clade containing all North American members (in subgenus Amerallium) are Eurasian taxa. Diversity within North America Allium is centered in the west, especially in California, and a number of species there are serpentine endemics (Nguyen et al. 2008).

Pollination Biology & Seed Dispersal.Gilliesia has very strongly monosymmetric flowers with only two stamens; the flowers may mimic insects (Rudall et al. 2002).

Vegetative Variation. The apparently bifacial leaves of at least some species of Allium have inverted vascular bundles along the adaxial surface and vascular bundles with normal orientation along the abaxial surface (Mathew 1996). In a comprehensive study, Mashayekhi and Columbus (2014) looked at the leaf anatomy of 67 species of Allium, i.a. species with terete, unifacial leaves might have a ring of bundles or a single series of normally oriented bundles, and species with flattened leaves sometimes had two series of nornally-oriented bundles.

Genes & Genomes. There has been a major movement of ribosomal protein and succinate dehydrogenase genes from the mitochondrion in Allium (Adams & Palmer 2003), and that genus has also lost its minisatellite telomeres (Sýkorová et al. 2006a).

Chemistry, Morphology, etc. The flowers of Allium are shown with the median member of the outer whorl in the adaxial position (Spichiger et al. 2004). Schickendantziella (Gilliesieae) has only three tepals; they are caudate. Coronal structures in Gilliesieae are variable and number of often more or less linear; they may be staminodial in some species, but it seems to me that this is unlikely where the number of stamens + linear processes = >6. Do Allioideae have apotropous ovules?

Some information is taken
from Sundar Rao (1940), Berg (1996) and Berg and Maze (1966), all embryology, and Rahn (1998: general). For Allium, see Rabinowitch and Currah (2002: more horti-/agricultural), Fritsch and Friesen (2002 [and many other papers in same book]: general), Fritsch and Keusgen (2006: cysteine sulphoxide distribution), and Choi et al. (2011: floral development, esp. epidermis).

Phylogeny. Fay and Chase (1996) discuss relationships
within the subfamily; the topology is [Allieae [Tulbaghieae + Gilliesieae]],
although the support for the clades is rather weak. Fay et al. (2006b) found that part of Ipheion was embedded in Nothoscordum. Nguyen et al. (2008) provide a phylogeny for Allium (see also Friesen et al. 2006; Hirschegger et al. 2010: section Allium; Huang et al. 2014); the relationships of members of the small subgenera Nectaroscordum and Microscordum are unclear (Nguyen et al. 2008; Mashayekhi & Columbus 2014). For relationships in subgenus Amerallium, which includes nearluy all North American species, see Choi et al. (2012), Li et al. (2012, and Mashayekhi and Columbus (2014: most sections not monophyletic). In the large subgenus Melanocrommyum of Allium there seems to be extended incomplete lineage sorting, and morphological sections are not supported by molecular data (Gurushidze et al. 2008, esp. 2010).

Classification. See Fay and Chase (1996) as Alliaceae. Friesen et al. (2006) provide a subgeneric and sectional classification of Allium which has since been elaborated (see above); Gregory et al. (1998) list names included in it. See Vosa (1975) for a revision of Tulbaghia and details of its cytology.

Amaryllidoideae are usually bulbous herbs that can be
recognised by their rather fleshy and two-ranked leaves and their scapose,
umbellate inflorescence of generally large flowers with six stamens and an inferior ovary.

Evolution.Divergence & Distribution. Meerow (2010) discussed diversification in American Amaryllidaceae in terms of the interplay of canalization and genome doubling, emphasizing the floral and vegetative diversity encompassed by the Andean tetraploid-derived clade. Santos-Gally et al. (2012) discussed the biogeography of the Mediterranean-centred Narcissus

Ecology & Physiology. Amaryllidoideae are an important component of the distinctive Cape geophytic flora (Procheŝ et al. 2006) having about 100 species endemic there. For water-catching leaves with very distinctive morphologies that are found especially in taxa from Namaqualand, South Africa, see Vogel and Müller-Doblies (2011).

Pollination Biology & Seed Dispersal. Monosymmetry is said to be ancestral in the subfamily (Meerow & Snijman 1998; Meerow 2010); it is certainly very labile, reversals and parallelisms being common, and it is perhaps under simple genetic control (Meerow et al. 1999). Some kind of corona is common, but its morphological nature varies (see below). The flowers are protandrous. A number of species of Amaryllis are heterostylous (Santos-Gally 2013 and references).

Bird pollination is quite important in Amaryllidaceae. A. Meerow (pers. comm. ii.2014) estimated that around 100-150 species of South American Amaryllidaceae (genera like Brunswigia, Hippeastrum, Stenomesson) may be pollinated by humming birds, while in southern Africa ca 13 species ofCyrtanthus alone are pollinated by sunbirds (Snijman & Meerow 2010) - several other kinds of pollinators service that genus.

Almost three hundred species in the subfamily have myrmecochorous seeds (Lengyel et al. 2010). Wind dispersal of the
seed is common in Amaryllideae, the rigid, radiating pedicels allowing the infructescences to bowl along in the wind. The testa is commonly massive, green and photosynthetic, and with anomocytic stomata in Amaryllidinae, while in Crinum, of the same tribe, it is the endosperm that is green and photosynthetic. Seeds of some species of Crinum lack a testa and may have a corky outer endosperm; such seeds can float and remain viable in sea water for up to two years, while seeds of other species lack the corky layer, sink fast and can germinate without very much in the way of water at all (Snijman & Linder 1996; Bjorå et al. 2006). In Boophone and Cybistetes the seeds germinate while still in the fruit, and in Calostemmateae the bulbil, a precociously-germinated embryo, is the dispersal unit. The inflorescence of Gethyllis (Haemantheae, includes Apodolirion) has a single flower; the ovary is subterranean and the many-seeded fruit is indehiscent and may be sweetly scented when ripe; dispersal by small mammals?

Genes & Genomes. García et al. (2014) discuss the likelihood that there was extensive and ancient hybridization in Hippeastreae-Hippeastrinae, although not in -Traubiinae.

There has been a reduction in the GC content of the genome here, perhaps associated with the large genome sizes also found here (Smarda et al. 2014).

Chemistry, Morphology, etc. Norbelladine alkaloids, unique to Amaryllidoideae, are tyrosine derivatives. There are over 200 different structures of which 79 or more are found in Narcissus alone (Martin 1987; Bastida & Viladomat 2002: other references in the same volume; Rønsted et al. 2008b. These alkaloids cause acetylcholinesterase inhibition, etc., in Hameantheae (Bay-Smidt et al. 2011) and Calostemmateae (Jensen et al. 2011). All told over 500 alkaloids placed in 118 different classes have been recorded from the subfamily (Rønsted et al. 2012); a number of species are poisonous because of them.

Because of the leaf fibres in Amaryllideae, the coverings of the bulbs produce highly-extensible cotton-like fibres when torn. There are often crystals of calcium oxalate in the
epidermis. Petiolate leaves have evolved at least six times in the family.

The flowers of Galanthus are shown with the median member of the outer whorl in the adaxial position (Spichiger et al. 2004), see also the similar position in Hippeastrum and several other monosymmetric Amaryllidoideae. Some species of Phaedranassa have slit-monosymmetric flowers, with all the stamens, etc., leaving the flower via an abaxial slit in the perianth tube; I do not know details of the symmetry there. Flowers of some species of Crinum are monosymmetric. In Galanthus in particular the inner whorl of tepals is very different from the outer whorl, although both are petal-like.

The corona of e.g. Hymenocallis, evascularized outgrowths of the filaments, and that of Narcissus, vascularized and tubular (see also Scotland 2013), but not associated with the stamens, are quite different (e.g. Arber 1937); the corona may also be a tube, sometimes toothed (Pancratium), on which the stamens are born. Haemanthus has tepals with a single trace. In Strumaria and Carpolyza the bases of the filaments are adnate to the style, while in Strumaria and Tedingia the base of the style may be much inflated, even bulbous. Flowers of Gethyllis have up to 18 stamens. It is unclear if some ovules are ategmic. Crinum has cellular endosperm. In Hymenocallis caribaea the ovule is crassinucellate ("pseudocrassincellate"), the micropyle is zig-zag, and the vascularized outer integument is massive (Raymúndez et al. 2008). x = 11 may be the basal chromosome number for the family (Meerow et al. 2006). A very long-tubular dropper cotyledon sheath may develop during germination.

For anatomy, see Arroyo and
Cutler (1984), for pollen, see Dönmez and Isik (2008), and for general information, see Markötter (1936: some South African taxa) and Meerow and Snijman (1998).

Phylogeny. Phylogenetic
relationships within Amaryllidoideae are [Amaryllideae [Cyrtantheae [Calostemmateae, Haemantheae, Gethyllideae [Eurasian Clade [Andean Clade, Extra-Andean Clade]]]]] (Meerow et al. 1999, 2000a, 2000b). Relationships between major clades of American and some southern African members are not well understood, furthermore, Meerow et al. (2006) found that the inclusion of Hannonia, Lapiedra and Vagaria destabilised relationships in the European clade; Lledó et al. (2004) included the last two in Galantheae. Meerow and Clayton (2004) discussed relationships among African taxa. In a more recent study using genes from all three compartments and sampling 108 species recovered the relationships [Amaryllideae [[Calostemmateae [Cyrtantheae + Haemantheae]] [Eurasian Clade [Andean Clade, Extra-Andean Clade]]]], although support for some nodes was poor; Gethyllis was embedded in Haemantheae (Rønsted et al. 2012: see classification above).

For a phylogeny of Cyrtanthus and discussion on its evolution, see Snijman and Meerow (2010); molecules and cytology, but less so morphology, tend to agree, and the old species groupings, based on floral (pollinator) morphology, have broken down. Meerow and Snijman (2001, see also 2006) discuss relationships within Amaryllideae; Amaryllis and Boophone are successively sister to the rest of the tribe. Amaryllis differs from other Amaryllidineae in not having a green testa, etc. Meerow et al. (2003) outline the phylogeny of Crinum, the only pantropical member of Amaryllidaceae; see also Kwembeya et al. (2007).

For relationships in Haemantheae, see Conrad et al. (2006) and Bay-Smidt et al. (2011). Meerow et al. (2006) provide a phylogeny for the Eurasian Clade, which includes daffodills, snowdrops, etc. The main dichotomy separates the Central and East Asian Lycorideae from the rest, which centre on the Mediterranean region. ITS and ndhF phylogenies are not congruent (Meerow & Snijman 2006). For a phylogeny of Galantheae and its alkaloids, see Lledó et al. (2004) and Larsen et al. (2010), and for that of Narcissus, see Rønsted et al. (2008b: acetylcholinesterase-inhibiting alkaloids) and Santos-Gally (2012).

Classification. For the infrafamilial classification of Amaryllidaceae, I follow Chase et al. (2009). For a classification of Amaryllideae, see Meerow and Snijman (2001, 2006), and for generic limits in Galantheae, see Lledó et al. (2004).

Botanical Trivia. The "Amaryllis" of many a windowsill is in fact a Hippeastrum.

Age. Divergence within the crown group began ca 89 m.y.a. (Janssen & Bremer 2004). Eguiarte (1995: Agavaceae and Nolinaceae), however, suggested an age of only some ca 47 m.y.a., Bell et al. (2010) suggested a crown-group age of (66-)56, 51(-42) m.y., while estimates in S. Chen et al. (2013) are ca 56.4 and 36.4 m.y..

Evolution.Divergence & Distribution. There are no obvious apomorphies for Asparagaceae s.l., however, "endosperm helobial, thick-walled, pitted, hemicellulosic" might be placed at this level. The homoisoflavanones found in Scilloideae are rather uncommon in flowering plants, but they are also found in Camassia (Agavoideae, ex Chlorogaloideae) and Ophiopogon (Nolinoideae).

Phylogeny. These seven subfamilies form a rather well supported clade in Fay et al. (2000). Fay et al. (2000), Pires et al. (2001), and Pires and Sytsma (2002) discuss uncertainties as to the immediate sister taxon to Themidaceae (= Brodiaeoideae). Aphyllanthes has a very long branch
in the three-gene analysis of Fay et al. (2000), and its phylogenetic position
is unclear; its removal from analyses can rather dramatically changes support values (Chase et al. 2006). A position close to Hyacinthaceae (= Scilloideae) was found by McPherson and Graham (2001), but Pires et al. (2006) place it sister to Laxmanniaceae (= Lomandroideae), albeit with weak support. [Themidaceae + Hyacinthaceae] appear a moderately well supported
clade in Fay and Chase (1996) and Meerow et al. (2000), but support in the two-gene analysis of Jang and Pfosser (2002: Aphyllanthes not included) is only weak (see also Chase et al. 2006; Pires et al. 2006). Seberg et al. (2012) found the relationships [[Brodiaeoideae + Scilloideae] [Aphyllanthoideae + Agavoideae]], but the position of Aphyllanthes had no support. Steele et al. (2012) also found Aphyllanthes associating with this group, but again with little support; there was good support for a clade [Lomandroideae [Asparagoideae + Nolinoideae]] (for this latter clade, see also Fay et al. 2000: moderate support; Seberg et al. 2012, strong support). For details of relationships, see also Bogler et al. (2006).

Classification. This is a highly unsatisfactory family. Nothing characterises it, and while some of the subfamilies have several distinctive apomorphies and are also easy to recognise, others are difficult to recognise. The flowers of the whole group are for the most part a rather undistinguished "lily"-type, and quite often are rather small. Asparagoideae, and especially Nolinoideae and Agavoideae, are very heterogeneous, several families having been segregated from them in the past. For the use of Asparagaceae s.l. to refer to the entire clade, c.f. A.P.G. II (2003) and A.P.G. III (2009). The subfamilial classification follows that in Chase et al. (2009b), but I have also included familial names for each clade, in part because the roots of the two sets of names differ in over half the cases and both will be encountered in the literature.

Aphyllanthoideae may be readily recognised. The above-ground plant consists of tufts of scapose infloresences, the scapes being the main photosynthetic organs since the scarious leaves at their bases are non-photosynthetic. The inflorescence is few-flowered, and the spreading, usually blue tepals are moderate in size - the plant looks rather like Sisyrinchium (Iridaceae).

Chemistry, Morphology, etc. The stomata are in bands down the
scape. The tepals have but a single bundle. Is there chelidonic acid?

General information is taken from
Conran (1998); he mentions helobial endosperm development here, but c.f. Schnarf and Wunderlich (1939), apparently the only source of embryological information.

Good-Avila et al. (2006) discussed diversification in both Agave, which they suggest may be connected with the adoption of bat-pollination, and Yucca (see also Rocha et al. 2006). Smith et al. (2008) suggested that diversification was not significantly different in Yucca, with 34(-50) species, and Agave, with some 250 or more species. They found little evidence that the adoption by Yucca of its remarkable pollination mechanism increased its diversification rate, although its sister group may be considerably smaller (see below). Pulses of diversification in agaves may have happened a mere 9-6 m.y.a., a time when other succulent clades were diversifying (e.g. Good-Avila et al. 2006; Arakaki et al. 2011).

Ecology & Physiology. Nobel (1988) discussed the eco-physiology of agaves and their relatives. Over 300 species are succulents, mostly leaf succulents (Nyffeler & Eggli 2010b); drought tolerance is common, and some species in the Chlorogalum area grow on serpentine soils, themselves often subject to drought (Halpin & Fishbein 2014).

Pollination Biology & Seed Dispersal. The Yucca-yucca moth (Tegeticula, Prodoxidae)
association has been a textbook example of mutualism or co-evolution, two partners showing reciprocal evolutionary change (see Althoff et al. 2012 for more details). The association may be some 40 m.y. old (c.f. the dates above, Pellmyr et al. 1996, 2007; Pellmyr & Leebens-Mack 1999; Pellmyr 2003; Gaunt & Miles 2002; Althoff et al. 2006), and there may have been another and more recent radiation of yucca moths only 3-2 m.y. ago. Close relatives of yucca moths also eat Dasylirion
and Nolina (see Nolinoideae) and other Prodoxidae are found on Saxifragaceae (Saxifragales); the ancestral condition for yucca moths may have been to eat ovaries (Yoder et al. 2010). Prodoxus, not a pollinator but a specialist herbivore on Yucca, and Parategeticula, another pollinator, are also involved. Much of the divergence in Yucca seems to have occurred before that of its main pollinator but only a mere 6-4 m.y.a., and given the vagility of the moth, it is difficult to imagine how strict co-evolution might work (see also Godsoe et al. 2010; Starr et al. 2014; Hembry et al. 2014). Initial diversification in Yucca may have been in association with Parategeticula, a poor flier and now rather uncommon (Althoff et al. 2012). For diversification in Yucca compared with that in its relatives, see above.

Bat pollination is common in the large genus Agave and its relatives (Fleming et al. 2009).

Genes & Genomes. For the connection between the evolution of the bimodal karyotype of Agave, Hesperocallis, and their relatives and polyploidy, see McKain et al. (2011, esp. 2012) and Halpin and Fishbein (2014). Thus Hesperocallis has 4 long, 2 medium and 18 short chromosomes, other genera have 5 long and 25 short chromosomes, and there are other combinations, but details of how bimodality interacts with polyploidy are unclear.

Chemistry, Morphology, etc. The raphides of Agave are hexagonal in transverse section. For variegation in Hosta, see Zonneveld (2007). The leaves of Herreria and Herreriopsis are described as being cladode-like (Conran 1998) or
cladodes (Stevenson in Takhtajan 1997).

The flowers of Agave are shown with the median member of the outer whorl in the adaxial position (Spichiger et al. 2004). Camassia at least has single-trace tepals, Agave, etc. have three, while Hosta may have as many as 13 (Lin et al. 2011). The outer tepals of Herreriopsis
have sac-like bases - possibly tepalline nectaries. The tapetal cells of Polianthes (= Agave) are multinucleate. In Hosta the stamens are sometimes inserted
on the ovary. Germination of the pollen grain via the proximal pole has been reported in Beschorneria (Hesse et al. 2009a). Furcraea has nuclear endosperm.

Traub (1982) noted that Hesperocallis undulata smells of onions, and he even associated it with his Alliales. The genus was geographically odd
in Hostaceae s. str., which is where other workers had placed it (c.f. Kubitzki 1998b), but not in Agavoideae as here circumscribed; now Hosta is a little odd from the geographical point of view.

The ovary and fruit of Leucocrinum (Anthericum group) are below the surface of the ground (Bogler et al. 2006). At least some mitochondrial genes show an accelerated rate of change (G. Petersen et al. 2006). Some information is taken from Conran
(1998); ovule morphology is known from Leucocrinum alone in the Anthericum group.

Ubisch bodies are present in Anemarrhena, so there
is probably a glandular tapetum. Information is taken from Conran
and Rudall (1998 - confusion over stamen position) and Rudall et al. (1998b). For information about Behnia, Herreria and Herreriopsis, see
Conran (1998); details of ovules/embryology are unknown.

Phylogeny. For relationships within this clade, see Pires et al. (2004) and especially Bogler et al. (2006: 2- and 3-gene analyses, the latter with missing data, but overall the same topology). I have followed the latter - which see for more details - in the topology above. Support for the subfamily as a whole is only 75%, that for the [Behnia + Herreria, etc. + Anthericum, etc.] clade 87%, and that for [Herreria, etc. + Anthericum, etc.] only 51% (and still less in the two-gene tree); however, other nodes have close to 100% support. Largely similar relationships were found by G. Petersen et al. (2006c) in their analysis of variation of four mitochondrial genes that are evolving particularly quickly in this clade. Smith et al. (2008) included Hosta, etc., in their Agavaceae and excluded Anthericaceae, although support for Agavaceae so delimited was weak; that for the still broader circumscription adopted here was stronger.

The circumscription of group 4b above, Agave, etc. + Hesperocallis, corresponds to that of Agavaceae s.l. in Bogler et al. (2006). Genera
like Camassia, etc. (ex Hyacinthaceae-Chlorogaloideae) are included here. There is a fair amount of resolution of relationships around Agave and Yucca; the former includes "genera" like Manfreda and Polianthes, and {Beschorneria + Furcraea] are sister to Agavae s.l., and while the position of Yucca is unclear, it might be sister to that combined clade (Bogler et al. 2006). Hesperocallis undulata was sister to the rest of the Agave, etc., clade (Bogler et al. 2006), although it has since been placed well within a clade that also includes Chlorogaloideae (Halpin & Fishbein 2014; see also Archibald et al. 2014, esp. 2015), and there Camassia is sister to Hastingsia. Halpin and Fishbein (2014) alsolooked at relationships in the old Chlorogaloideae and found that Chlorogalum itself was paraphyletic (see also Archibald et al. 2015). For other phylogenetic work on this group, see also Eguiarte et al. (1994), Bogler and Simpson (1996: molecular) and Sandoval (1995: morphological).

Classification. The broad concept of Agavoideae adopted here may not seem very satisfactory, but none of the alternative solutions is any better. Agave should probably include Polianthes, Manfreda, etc., see e.g. Bogler and Simpson (1995), Bogler et al. (2006) and Rocha et al. (2006).

Previous Relationships.Paradisea (ex Asphodelaceae/Xanthorrhoeaceae-Asphodeloideae) is a member of the Anthericum group (e.g. Chase
et al. 2000b). Behnia was included in Luzuriagaceae (Liliales here) by Taktajan (1997), but it has also been placed in other lilialean and asparagalean families (Bogler et al. 2006).

Asparagaceae-Brodiaeoideae are like Amaryllidaceae-Allioideae in their scapose,
umbellate inflorescence, often rather small flowers, more or less connate tepals
sometimes with a corona, and a superior ovary, but the plants have a fibrous corm, not a bulb, and
lack the distinctive smell common in the latter family, and there are usually
4 or more inflorescence bracts that are not all-enveloping like the ca 3 bracts
of Allioideae.

Chemistry, Morphology, etc. Little is known about the chemistry of Brodiaeoideae.

When the tepalline tube is adnate to the stipitate gynoecium, three narrow, ?nectar-containing tubes are formed. Embryologically Brodiaeoideae are quite variable. The inner integument is massive or
not, ditto base of the nucellus, endosperm development varies, etc. (Berg 2003 for a summary).

Phylogeny. There are two major clades, [Muilla, Triteleia] and [Dipterostemon, Dichelostemma, Brodiaea], albeit with only moderate support. The first clade has a long tepalline tube and the second has appendages on the bases of the filaments that form a nectar cup; both characters arise in parallel in the opposing clade (Pires & Sytsma 2002; c.f. Seberg et al. 2012). See also Pires et al. (2001) for phylogeny and morphological evolution.

Previous Relationships. Themidaceae/Brodiaeoideae have often been included in Alliaceae/Amaryllidaceae-Allioideae because of their superficially similar umbellate inflorescence and rather undistinguished monocot flowers (e.g. Takhtajan 1997).

41-70[list]/800-1025 - six groupings below. Predominantly Old World, Mediterranean climates, esp. S. Africa and
the Mediterranean, to Central Asia and Japan; a few in South America (map: both colours).

Age.Oziroë diverged from the rest of the clade in the Oligocene ca 28 m.y.a. (Ali et al. 2012).

Scilloideae are bulbous monocots with rather fleshy, mucilaginous leaves that are all basal. The scapose, racemose inflorescence bears for the most part rather undistinguished monocot flowers with more or less connate tepals; the fruit is a capsule.

Evolution.Divergence & Distribution. Divergence in the rest began only ca 18.8 m.y.a. early in the Miocene. The subfamily may have originated in sub-Saharan Africa and dispersed north and also east, but details depend on the analytic method used (Ali et al. 2012). There are about 300 species of Scilloideae in the Cape flora alone (Procheŝ et al. 2006).

Ecology & Physiology. Many species in the foggy deserts of Namaqualand, South Africa, have water-catching leaves with very distinctive morphologies (Vogel & Müller-Doblies 2011).

Pollination Biology & Seed Dispersal.Lachenalia has monosymmetric flowers in which the median member of the outer whorl is in the adaxial position. The same is true of the remarkable monosymmetric flowers of Massonia (Daubneya) aurea that are on the outside of the inflorescence. These flowers have the three abaxial tepals greatly enlarged, while the inner flowers are polysymmetric, the tepals forming a simple, lobed tube; the result is an inflorescence looking like a flower. Pollination in Albuca is noteworthy in that the pollen is deposited by leaf-cutter bees on the tips of the inner tepals, pollination not being completed until two to three days later when the flower withers, the tepals press against the stigma, and the pollen finally germinates (Johnson et al. 2009b, 2012).

Species with myrmecochorous seeds are scattered throughout the subfamily (Lengyel et al. 2010).

Chemistry, Morphology, etc. Some species of Scilloideae have terete, unifacial leaves, as in Ornithogalum, where they develop from the upper part of the leaf (Kaplan 1973). Even the bulb scales of some species of Rhadamanthus (= Drimia) are terete. Urgineeae have a backwardly-directed process at the base of the leaves and/or bracts (c.f. Asparagus: Asparagoideae). Vegetative variation - in both leaf and bulb - is also considerable in Ledebouria (Venter 2007). However, there is less anatomical variation; although mucilage cells are particlarly common in Scilloideae, they also occur elsewhere (Lynch et al. 2006).

For some floral vasculature, see Deroin (2014). Some Scilloideae have a filament tube. Wunderlich (1937) described the endosperm as being both helobial and nuclear in Hyacinthineae. Karyotypes may be bi- or even trimodal. The leaves of seedlings are two-ranked.

Information is taken from
Speta (1998a: subfamilial classification of Hyacinthaceae, 1998b: general, 2001: subfamilial characters) and Pfosser and Speta (1999); for chemistry, see Kite et al.
(2000), Pfosser and Speta (2001) and Koorbanally et al. (2008), for anatomy, see Lynch et al. (2001), for some embryology, see Sundar Rao (1940), Eunus (1950) and Berg (1962), for floral morphology in Ledebouriinae, see Lebatha and Buys (2006), and for cytology of some sub-Saharan members, see Goldblatt and Manning (2011) and Goldblatt et al. (2012: base numbers for tribes, etc.).

Phylogeny. The topology [Oziroëeae [Ornithogaleae [Urgineeae + Hyacintheae]]] has moderate support in Manning et al. (2004); Oziroë and Albuca (Ornithogaleae) were successively sisters to the rest at the base of Scilloideae in Seberg et al (2012), the position of the latter genus having only moderate support. There is little well-supported structure along the backbone of Hyacintheae and again within Hyacinthineae in the trnL-F spacer analysis of Wetschnig et al. (2002); the positions of Ornithogaleae and Urgineeae were also unclear. See also Pfosser et al. (2003, 2012), the latter dealing with relationships of the Malagasy taxa.

Classification. For a classification, see Speta (1998a: as Hyacinthaceae). There is considerable disagreement over generic limits here; are there 15 or 45 genera in sub-Saharan Africa? (e.g. Stedje 2001a, b; Pfosser & Speta 2001; Lebatha et al. 2006). See Speta (1998a) for the dismemberment of Scilla and Martínez-Azorín et al. (2011) for that of Ornithogaleae - 19 genera, of which 11 replace Ornithogalum; recognizability of taxa is not the issue. Manning et al. (2004) provide a generic synopsis of the family in sub-Saharan Africa that integrates some morphology with relationships; like them, I take a generally broad view of genera. However, there are unresolved issues that include sampling, whether or not floral syndromes distort ideas of relationships (and so what effect characters taken from these syndromes have in combined analyses), the consequences of maintaining well-known generic names like Albuca and Galtonia as knowlege of phylogeny becomes clearer, and the role cytological data should play. Albuca is recognized in the recent reclassification of Ornithogaloideae by Manning et al. (2009).

Previous Relationships. Chlorogaloideae, until recently included in Hyacinthaceae/Scilloideae (e.g. Pfosser & Speta 1999), are here included in Agavoideae.

Chemistry, Morphology, etc. There are reports of cell
wall ferulates from Xerolirion (Rudall & Caddick 1994), which, if true, makes it about the only non-commelinid genus with them. In Thysanotus roots, fungi are associated with the subepidermal layer of cells (McGee 1988).

Eustrephus has vessels in its leaves. The leaf of Lomandra and its relatives has sclerenchymatous ribs
extending from the inner sheath of the vascular bundles (c.f. also Cordyline?), in Dasypogonaceae this
sheath is absent, in Xanthorrhoea it comes from the mesophyll, although the
leaves of all three are xeromorphic and superficially similar (Rudall & Chase 1996).

Xerolirion has solitary,
terminal carpellate flowers, while its staminate flowers are in cymes. The pollen of Lomandra is
very variable, sometimes being spiraperturate (c.f. Aphyllanthes). There is considerable variation in seedling morphology, even within individual groups (Conran 1998).

Baccate fruits containing seeds that lack phytomelan are common here, but I do not know where they might be apomorphic. Since the capsular Hemiphylacus and [Comosperma + Eriospermum] are respectively sister to other Asparagaceae and Ruscaceae, baccate fruits are probably derived several times (c.f. Judd et al. 2007).

Age. The start of divergence within crown group Asparagoideae can be dated to ca 16.4 or 9.6. m.y.a. (S. Chen et al. 2013).

Evolution.Divergence & Distribution. Fukuda et al. (2005a) discuss diversification in Asparagus; this seems to have been rapid and to have started in southern Africa. Hybridization between species seems common in the dioecious subgenus Asparagus (Kubota et al. 2011). Species of Asparagus with flattened cladodes have perfect flowers (Kubota et al. 2011). Asparagus is quite often found in drier/sandy habitats.

Vegetative Variation. There has been much discussion as to what the more or less leaf-like structures in the axils of the leaves in Asparagus "are" - stem or leaf or something else? (see e.g. Arber 1924b - prophyllar, axial; Cooney-Sovetts & Sattler 1986 - homeotic). Nakayama et al. (2012, see also Nakayama et al. 2010) looked at the development of both leaf-like and terete cladodes in Asparagus. The former (A. asparagoides) had an inverted (= prophyllar) orientation, while the latter (A. officinalis) were ventralised (c.f. Allium). They noted that both "leaf" and "stem" genes were expressed in the cladodes; the gene regulatory network for leaf development had been coopted by the axillary shoot (Nakayama et al. 2013).

Chemistry, Morphology, etc. Methyl mercaptans are known from Asparagus.

The prophylls ("bracts") at the
bases of the pedicels in Hemiphylacus are described as being lateral
(Hernandez S. 1995). For floral development in Asparagus, see Park et al. 2(003, 2004); b-class genes are not expressed in the outer tepal whorl.

Some information is taken from Robbins and Borthwick (1925: ovule and seed), Kubitzki
and Rudall (1998: general) and Rudall et al. (1998b).

Phylogeny. For phylogenetic relationships in Asparagus, see Fukuda et al. (2005b) and Kubota et al. (2011); subgenus Myrsiphyllum, at least, is probably paraphyletic. The placement of Eriospermum (Nolinoideae here) as sister to Asparagoideae has quite strong support (Seberg et el. 2012); this position must be confirmed.

Previous Relationships.Hemiphylacus used to be placed in Asphodelaceae (Xanthorrhoeaceae-Asphodeloideae).

Evolution.Divergence & Distribution. Biogeographical relationships in the the Dracaena group are of considerable interest. Pleomele (= Chrysodracon) from Hawaii is sister to the rest (e.g. Lu & Morden 2010, 2013, 2014), which raises all sorts of biogeographical questions (shades of Hillebrandia?), and in turn Central American species are sister to the remainder. There seems to have been extensive dispersal (and extinction) in this whole clade (Lu & Moprden 2014). Lu and Morden (2014) noted several independent transitions to the arborescent habit (perhaps four times) and the development of cylindrical leaves (ca seven times).

Pollination Biology & Seed Dispersal. The flowers of Aspidistra, sometimes borne beneath the litter, often have a large, fungiform stigma, the anthers being hidden below it (Endress 1995b: floral morphology), or the anthers converge towards the centre of the flower; in both cases easy access to the nectar is apparently blocked. It has been suggested that such flowers are pollinated by amphipods (Conran & Bradbury 2007 and references), or fungus gnats; Megaselia, a phorid fly (Vislobokov et al. 2013), as is a non-galling cecidomyiid midge, which also lays eggs in the nthers, the larvae eating the pollen (Vislobokov et al. 2014b). Flowers of somes species of Aspidistra look rather those of some Aristolochiaceae or Burmanniaceae. Other species have more conventional sub-rotate flowers with the stamens and stigma/style grouped in the centre, or they have a short corona at the apex of the perianth tube, while yet others have a balloon-like perianth with a little opening at the apex. There may be anything from two to a dozen or more tepal lobes (see also Hou et al. 2009; Li 2004; Vislobokov et al. 2014a). A remarkable genus!

Vegetative Variation. Vegetative variation is particularly impressive. Dracaeana is the only monocot known with a monocot cambium in its roots (Carlquist 2012a). Nolina (ex Nolinaceae) has secondary growth in the stem and is tree-like, Beaucarnea, also tree-like, has a much swollen stem base, while the initiation of the vascular system in the rhizome of Ophiopogon is similar to that in palm stems (Pizzolato 2009).

The leaf blades of some species of Eriospermum have the most remarkable enations on the upper surface. These include fungiform protrusions on the small, crisped, ovate and fleshy blade (E. titanopsoides), a much-branched structure to 12 x 7.5 cm on a much smaller blade (E. ramosum), a bundle of enations with stellate hairs (E. dregei), and paired enations that look as if they should grace the helmets of the Valkyries (E. alcicorne: see Perry 1994 for more details). These may be adaptations for catching water from fog (Vogel & Müller-Doblies 2011). The fleshy leaf of Sansevieria (= Dracaena) is developed from the leaf base, the apical portion of the leaf being represented by a Vorlaüferspitze (e.g. Kaplan 1997, vol. 2: chap. 16); depending on the species, the leaf can be developed predominantly from the base (and is flattened) or from the apex (and is terete: Kaplan 1973). Many other taxa, including Maianthemum, have more or less broadly elliptic leaf blades.

Ruscus and its immediate relatives have cladodes, the flowers being born in the middle of a tough, more or less elliptical leaf-like structure. The prophylls are lateral or in some interpretations completely adnate to the axillary shoot,
together they form an expanded cladode (Arber 1924a, 1930), or they are homeotic structures (Cooney-Sovetts & Sattler 1987). In any event, the leaves proper are small and scarious and subtend the cladode-like structures (c.f. Asparagus above).

Peliosanthes teta, the only species in Peliosanthes, has an ovary that varies from superior to inferior (Jessop 1976: some recognise more species in the genus). The absence of
septal nectaries in some Nolinoideae may be connected with the presence
of prominent ovary wall obturators; the latter are possibly derived from the former. In Liriope, etc. (Ophiopogoneae), the seeds, with their fleshy testa (see above), are exposed early in development, so they are semi-gymnospermous.

Phylogeny The placement of Eriospermum (for which, see Perry 1994) as sister to Asparagoideae has quite strong support (Seberg et el. 2012); it and and
the very distinct Comospermum are likely to be sister to the rest of the family; both have
capsules and hairy seeds. Note, however, that the hairs on the seeds of the two genera develop in different ways, and Comospermum has two tenuinucellate apotropous ovules/carpel, n = 20 vs. n = 7, etc.; the two genera would at first sight seem to be unrelated (Rudall 1999). The poorly understood Peliosanthes
may also be in turn sister to the rest of the family (molecular data alone, e.g. Jang & Pfosser 2002), although G.-Y. Wang et al. (2014) suggests that it is a member of Ophiopogoneae, a group in which capsules open precociously before the seeds are mature (see also G.-Y. Wang et al. 2013). None of these genera was even sub-basal in the study of Seberg et al. (2012), while Eriospermum even linked up with Asparagoideae.

Relationships within other Nolinoideae are poorly resolved, although major
clades seem to correspond largely with tribes (see Conran & Tamura 1998). However, Convallarieae may be paraphyletic with Aspidistreae and Ruscus and relatives
embedded (Yamashita & Tamura 2000: Eriospermum not included;
Rudall et al. 2000b); in Ruscus and immediate relatives a mitochondral cox2 intron is missing (Kudla et al. 2002). Meng et al. (2014) discussed relationships within Polygonatum and its relatives (Polygonateae). For relationships of ex-Nolinaceae, -Dracaenaceae, etc., see also Bogler and Simpson (1996). Dracaena can be circumscribed to include most of Pleomele and Sanseviera, with Pleomele from Hawaii (= Chrysodracon) is sister to the whole of the rest of the group (e.g. Lu & Morden 2010, 2013, 2014); this clade may be sister to Ruscus and relatives. Rojas-Piña et al. (2014) evaluate relationships around Beaucarnea and Nolina; there are three morphologically distinctive clades of tree-like plants there, although support for the monophyly of Nolina is not strong.

Classification. There has been debate over the generic limits of Maianthemum, however, a broad circumscription seems appropriate; there is little support for infrageneric groupings within the clade that also includes Smilacina and the combined clade itself is well supported as being monophyletic (Kim & Lee 2007; Meng et al. 2008).